Welcome! I’m new here too, not a bunny owner yet, but I may be able to answer some questions from the research I’ve made!
It is recommened to give unlimited alfalfa pellets to a young rabbit. Once they start reaching 4-5 months of age it is also recommened to start slowing down and decreasing the amount of alfalfa pellets and slowely introduce adult rabbit pellets. Do not make sudden changes when it comes to your bunnies diet as it can affect their digestive system a lot.
Some people put hay inside of the litter box in the very front. This may create more waste hay but it would definetly help with litter training!
Do keep in mind that you shouldnt hold a bunny for your pleasure, they hate being picked up. Only hold your rabbit if you aren’t acctually picking them up and if you aren’t forcing him to stay by you. This may be the reason he is peeing and pooping on you, if he can’t get to his litter box then he has to go right there!
Also to help you with litter training, make sure you are picking up his poops, and put them in the litter box. Also wipe up his pee with a paper towel and put the paper towel in the litter box. Also make sure the litter box is in a corner as bunnies like to do their business and eat in corners.
Hope I helped and I wish you good luck with your new bunny!