oh wow...I know its been a few days now and I hope the kitty is doing ok. As stated above...yes the kitty definately needs to eat and syringe feeding sounds like the only option right now. I'm actually shocked the vet didn't keep the kitty hospitalized and on an IV due to having to reattach both the nose and jaw. I would be concerned with breathing complications since those are the only airways!!
Hopefully you have been able to get food into him and liquids. There is a product called Nutracal which you can get at most pet stores that may also help. Its a gel you can put on the gums and has a high nutritional content. Works great on sick kittens and cats that won't eat. If syringe feeding isn't working, as I worry with the jaw issue, then this kitty needs to be hospitalized with a feeding tube. Or at least a feeding tube put in and then you given instructions how to feed and care for it at home.
Hi Sheilla and Welcome...you are right to be worried and kitty needs some nutrition ASAP. Here is a link from our Health Pages on how to *Syringe Feed* this kitty. I am shocked the vet didn't give instructions. I'm not going to say anymore because you need to begin reading this link and get the supplies listed. Just click on the blue link below...
http://www.medhelp.org/health_pages/Pets/Syringe--Force-feeding-for-cats--Part-one/show/491?cid=2
You can also Google "How to syringe feed a cat". I came upon several videos. I thought I had a link to a video, but I can't find it. Please let us know how kitty does and Good Luck!