Does the tumor feel soft and squishy? Often a tumor that size, if it were cancer, would have spread by now, and you'd be looking at pretty terminal symptoms. It sounds very much to me like it could be a Lipoma (a harmless fatty tumor) You need to ask your vet about this. If you wish, this could be needle-biopsied to confirm it (which would only be a quick visit to the vet, and wouldn't need anesthetic)
If it IS one of those, you (and her) can more or less forget about it. It might sound gross, but it is my bet it won't cause too many issues.
As for the weeping moles....what does your vet say about them? Does he/she think they are cancerous? Or just regular moles? If so are they chronically infected? Is that why they are open and weeping?
A good topical antibiotic cream might help that.
I will tell you something that works on any open sores, and works like a dream...and that is Echinacea Angustifolia Herbal Tincture. It is perfectly safe for dogs. The only time it shouldn't be used is either: in combination with antibiotics, and if the dog has an auto-immune condition.
A dog who is eating, happy, still having some fun in life, and seems not to be in pain or constant discomfort, is not ready to go yet.
You ask...Is it time...?
I can tell you from personal experience, that if you are not sure wheather it is time or not to euthanize you dog,
Then, it is not time.
You know your dog best, I am sure you know this dog, as well as the other 3 that you mentioned. If you knew it was time for them to go, then you will also know when it is time for this dog.
If your dog is not suffering, and has not been diagnosed with a malignant cancer.... or is not continually sick...then, If it were my dog...I guess I would wait till I saw a change for the worse...and enjoy what time I have left with her.
Bring her in for regular check ups...and ask your vet for his opinion.
In the meantime...you just keep doing the best you can, and give her lots of hugs.
I have read tumors in dogs just grow, but always spread through it's
body. Have you had blood test or biopsy? It may not be cancerous and
if it is, I've read these fatty tumors don't usually spread. Your dog may be just fine, if she acts normal as long as you follow your Vet's advice. Dogs will show pain when they are hurting.They let you know, at least my Jack show me and we give him his meds. We had a dog who was diabetic and had to give her shots twice a day for 5 years. She was so good taking her shots, we always gave her a treat afterwards...she lived past 15 years. I would take it one day at a time. Sounds like she is hanging in there and you are doing you're doing your best for her. Take care,
Mark