It is about that time to feed him about 1/8 a cup a day of pellets cause he is so little. However I would be slow in doing that cuz he is still somewhat young. Timmy hay and pellets usually start at 6mos I believe starting them on timmy at about 7 mos good rule of thumb there.
Of course unlimited hay. You sound like you are doing good with his food already. Gosh no pellets at the humane society oh yi. Yeah they dont ‘know a whole lot about rabbits yet probably.
He must have inhaled those pellets when you fed him too. Sounds like he is going to get much better care now.
The green tabs up top has a bunny into tab under it will be diet you can choose that option and get a better idea.
Also houserabbitsociety has good info on feeding them and good and toxic vegies fruits list too. This might help you out too.
I read that for every 5 lb feed 1/2 a cup. MIne are under 5lb actually 3 & 4 lb. I feed a little less than 1/8c 2x a day. They seem fine with this and are eating more hay which is good. Cotton was scarfing the pellets and not paying much mind to the hay.
Not anymore.
I am sure you will find what amount is best for your furbaby too.