Hi. Okay, there's a lot to talk about here, so bare with me.
Firstly, thank you for rescuing him. And that's on behalf of all dog lovers throughout the world ... and Bebe herself. By coincidence, my own rescued lurcher, named BB (yes honestly) is why I started to learn about canine kidney disease many years ago. Sadly, BB is no longer with me, but her legacy lives on in every message I make, which is now scores every day on so many websites.
I think your vet has got some things right - and some things wrong. But do remember I am not a vet, so it's up to you who you listen to and what actions you take.
I think he could be right about fluid therapy. This can be extremely tricky when a dog has a heart problem, but it is more risky with dogs that have congestive heart failure, which I am not so sure is the diagnosis here. Fluid therapy is the first line of treatment for most dogs in severe creatinine abnormality, so it's definitely something you should discuss further with your vet (or preferably a vet with good heart condition knowledge and experience), because it will become a much more important consideration in due course as the kidney disease deteriorates (but see below).
The original dental issues are potentially a reason why the kidney disease began. Dental disease is the most common cause of canine kidney failure. The infection and bacteria from bad gums and teeth over a prolonged time period goes down the gut and eventually to the kidneys. As the immune system becomes affected, the kidneys cannot cope with all this bacteria and start to shut down - and that starts a process that leads to chronic kidney disease.
While the Clindamycin no doubt helps, unfortunately all antibiotics add stress to the compromised kidneys, which have to try and deal with the by-products of the drug while it is being metabolised. This added stress can make the kidney disease deteriorate that much faster, but it's a difficult decision whether to give or not, because there are both pros and cons involved.
Theophylline is metabolized extensively in the liver (up to 70%). The remainder is metabolized by the kidneys. That's quite good, because the liver is probably more able to deal with things than the kidneys (many drugs are metabolized only by the kidneys). However, like all drugs, there will still be some added stress to the kidneys. In addition, as the liver is required to take over some of the functions of the deteriorating kidneys, this also puts a strain on the liver. At the very least, you need to start giving Bebe some supplemental protection, such as Milk Thistle.
Glucosamine is another problem. It can cause kidney failure and/or cause a rapid deterioration of any existing kidney failure. On the other hand, it no doubt eases the painful joints, so hard decision to give or not give. This really is a quality of life decision only you and your vet can assess.
Creatinine at 2.4 would put Bebe in Stage 3 of kidney failure. This is the appropriate time to start fluid therapy in most dogs, which would help reduce the creatinine maybe bringing the kidney disease back to stage 2. As outlined earlier, it would be appropriate to undertake a careful risk assessment preferably with a specialist vet.
Phosphorous at 6.3 means it is just in the abnormally high region - and NOW is the time to start an effective phosphorous binder. My advice is to use aluminium hydroxide gel powder (you can actually buy this from places online such as ThrivingPets, which will be way cheaper than through your vet - but you may need a vet's prescription for it - some countries need it, others don't). This is the most effective of all the binders available and is best started early rather than late. It must be given with food and the dosage is dependent on weight of dog (ask if you need advice on dosing).
In addition to the binder, the diet needs assessing, so that phosphorous content in food is reduced as much as is possible.
Amylase is high, which means your dog has pancreatitis. Did your vet mention this? An inflamed pancreas can be very painful and is made worse by fatty dog foods - so reduce all fat in food as much as possible until the pancreatitis is resolved. Antiemetic medication is useful to prevent vomiting - particularly important with kidney disease dogs, as that can lead to further dehydration. It would be useful to get lipase checked in a new blood test.
WBC is within normal range, but at the higher end. This would be indicative of an infection being resolved - or one starting up. Did the vet do a Culture and Sensitivity urine test? If not, I would have it done (you can catch a mid-stream specimen yourself and take it in, so Bebe isn't stressed by having to go to the vet). The result will disclose whether there is a urinary tract infection (UTI) and if there is then the C&S test will also provide the best antibiotic to solve it.
Omeprazole will help against acid-reflux, which is a major cause of nausea in kidney disease dogs (and why many turn their noses up at all food). The Cerenia is a good choice, and this helps deal with other nausea issues. Both the Omeprazole and Cerenia should continue to be given.
Very important ... has your dog been checked for tick-borne infections/viruses? This can be the start of an acute episode of kidney failure. If Bebe has not been checked, make sure your vet undertakes it asap.
I assume your vet also checked blood pressure? If not, again, this is extremely important. 90% of kidney failure dogs have high blood pressure, which makes the disease progress significantly faster.
Dry dog food (of any kind) is the very worst dog food you can give a kidney failure dog. To cut a long story short, it is less nutritional, has masses of chemicals and preservatives, and more importantly, it does the reverse of what's actually needed by dehydrating the gut and gastric tract - thus making the kidneys even more stressed. It has been proved beyond doubt that long-term use of dry foods (without enough pre-watering) actually causes canine kidney failure.
The best food (other than home cooking) is a suitable kidney specific canned dog food. I tend to suggest Hills kd canned, only because I am more familiar with it. It contains 80% water, has restricted protein and low phosphorous - all the qualities your dog needs right now.
There are a couple of supplments you might want to start, which will also help ... CoQ10 and Pure Organic Salmon Oil (salmon oil must always be given with a Vitamin E supplment, as it depletes this vitamin in the dog's body). All supplements should be canine formulated, not human varieties.
Okay, well, there's a lot to take in there I guess. So, have a think, adapt diet, discuss things with your vet, get the additional tesing done and get back to me when you can.
My little Yorkie also has kidney failure and enlarged heart. He takes pimobendan, enalypril, and phos binder. I too was told he would not be able to handle subq fluids. In May he got extremely dehydrated and the vet gave him 75 ml of subq fluid and I continued it for one week, then 50 ml every other day for one more week (if I recall correctly). Once we stopped the fluids, he got dehydrated again. So with vet permission we continued the 50 ml every other day. It has been over 6 months and he is handling it very well. Ask your vet if a low amount can be administered and have them monitor him. It gave my dog a few months of quality. I thought I was going to loose him when he got dehydrated.