I think you’ve got a pretty good plan in place. What type of lettuce are you feeding? Finn’s veggie diet is pretty much the same as what the pigs get, save for a few adjustments. I try to keep the main base as a lettuce, but I rotate the type, and I try and feed at least 3 different types a day. So in the morning they may get escarole and a few raddichio leaves, then in the evening they may get green leaf or butter lettuce as an example. Then it’s typically a few slices of bell pepper, which I know you said your buns aren’t fond of. Anything else is an “extra”. So I may do a few radish chips, a baby carrot, an herb such as coriander, parsley or dill, or a couple pieces of fennel. I mix those up and offer something different at each meal, since I split my daily veggies in half. They get part in the morning and part in the evening.
I have never used alfalfa hay with any of the pigs or with bun. I was taught if you’re feeding alfalfa pellets, you don’t NEED to feed alfalfa hay. It can be difficult to ween them off the alfalfa, and sometimes even mixing…some buns will pull out and scatter everything but the alfalfa. If bun is old enough to be introduced to veggies and is eating them comfortably, you an make up for not feeding alfalfa by including veggies that are higher in calcium. Parsley is an excellent source of calcium. I bonded an 8 week old guinea pig with a 3 year old pig, and since an adult guinea pig shouldn’t be eating alfalfa hay or alfalfa based pellets, same with adult buns, I had the baby on an adult diet (timothy hay and timothy based pellets) and would bring him out separately for extra parsley so he was getting a bit more calcium. He’s six months old now, and on his way to being my biggest pig. And not in a fat way. He’s just a very solid, healthy, big baby pig. This is just the way I’ve handled hay though, and it’s worked for my current herd. Alfalfa is a legume, not a grass hay, which is what adults need, and it’s also high in calcium. This is why it’s recommended for growing kits and pregnant/lactating does. Too much calcium in an adult can cause kidney and bladder stones.
As far as the pellets go, if your kit is is getting unlimited pellets and he’s not finishing them all quickly and is still eating hay, then he can probably continue on the unlimited until he’s about 5-6 months. I cannot offer unlimited pellets to Finn, because he is a pellet fiend. He’ll attack the bag when you’re filling his dish if he can get to it, and he will eat 1/4 of a cup in a matter of hours. He gets 1/4 cup in the morning, it’s usually gone within 2-3 hours and he has access to hay for the remainder of the day. I’ll put another tablespoon in the dish before bedtime for him to have in the pen. I usually keep timothy and meadow hay in the cage, and then sometimes I mix in either orchard grass or botanical hay for something extra. If he had unlimited pellets, he would never eat hay. So the vet and I decided it was in his best interest to not unlimited feed on pellets.