He is adorable!! Welcome to a wonderful home Patches!

I feed my cats different than most people. They always have dry food in their bowls. This works for now since they are both at good weights. I couldn't do that with my RB kitty Taz. He got too big on free feeding.
I also give my two kitties 1/8 of a can of wet food each day. They usually eat it all up in about 10 minutes (long enough for me to do my daily stretches), then I pick up the plates and wash them. If he seems to not be eating the entire 1/8 of the can maybe give him less for now until he gets bigger. But just keep an eye on him and if he seems to be getting "plump" then cut back on his amount of food. Or if he seems a bit thin then give him more. This is also how I manage the dogs weight. The bag might give suggestions on how much to feed, but those aren't set in stone. I think all cats are different...just like we are.

I can't wait to see more pictures of Patches! (hint hint)