Wow! What a list of questions!
First of all, welcome to the wonderful world of Persians and bless you for rescuing a kitty from a shelter. Let's see what I can do to answer some of these....
A metal comb is best. If possible, get a greyhound comb. They are not cheap, but are REALLY the best you can use. Slicker brushes and short=tined combs don't get down to the skin and that is esssential. You also want a blunt tip pair of scissors for mats that might develop and can't be worked out with the comb or your fingers.
I've never used mentholated ear-cleaner, so I don't know about that one - unless it creates an allergy, it should be fine. Those tufts in thier ears is a wonderful Persian trait, so I wouldn't ever clip them. The same for those tufts on their feet. I've never had a mat there - kitties are pretty good about keeping their feet mat-free.
Shaving your kitty is a personal preference. Giving him a lion clip when he comes home to you is fine to even things up, but don't shave his tail if possible. It takes FOREVER to grow back.
Food is another highly personal preference. I think the diet you are planning sounds like a great start! If possible, you might want to start with the kibble he is eating now -- a new home and new food is a big adjustment.
Sanitary shaves are a great idea. Without them, you might be giving more potty baths than you like.
I'll let someone else answer the shampoo question -- I don't bathe Sasha myself. One thing I do know, though, is that rinsing of it out is essential!
Unscented baby wipes will do for cleaning his eyes -- I know a lot of members use cotton pads and a multi-purpose contact lens solution. If he has discoloring or staining from the tearing, Eye Envy is a great product.
You sound like the perfect owner for this boy -- I wish you lots of love and luck with your new Persian. Be sure to let us see a picture when you bring him home.