Hi!! Kitty harness should be fine, mini rexes are a plumper breed. Think Labrador retrievers and beagles (in dog comparison) so the harness should fit him nicely. The ceramic dish seems untippable so you're awesome there!
I had dragged up reviews of the food online before I saw you returned it. I don't see a need for the gimmicky extra bits of hay.. He should eat like 97% more hay than what that food offers!! lol I know you know that but some people might think that it has enough hay and not buy a separate bag :/ Anyway, the juvenile kind is good :) Try to compare it with this brand : http://www.oxbowanimalhealth.com/pro...il?object=1543
Oxbow is the best brand and I chose my brand based on its GA to this food. (Acacia doesn't really like Oxbow, so Martins has comparable quality) Kaytee is probably fine as long as it's got high fibre content and low sodium/fats/bad proteins. (*goes to find kaytee juvy food ga)
Your grate on wood idea is fantastic! It won't harm him (just keep his nails trimmed) and it will prolong the life of the wood shelf!! YAY. (Never thought of that earlier)
The Kaytee juvy food is a bit low in fibre, so make sure he eats tonnes and tonnes of hay and no treats!! (only hay based treats)
So he knows he's getting the bunny?? Shucks! Oh well. Now the stress can be shared between you two as you shop together!
One more note, The Carefresh is one of the best litters out there, however, in order to litter box train- he will need a dfferent substrate (if you will) in the litter pan so he can tell the difference. I use shredded newspaper but mini rexes have less hair on their hocks and consequently I ran into some infections. Yesterday's News is a good one but if you find something else make sure it won't impact if digested (corn, crystal, clay litters are a big no-no)
I'm getting excited!! When are you picking up the little baby?