Hello there, what a surprise that must have been! It sounds like bunny is in good hands though as you are doing plenty of research
Alfalfa hay is good for buns under 6 months old though it can be tough to transition them off of it. So you can also feed a grass hay at this time too (timothy, meadow, orchard, oaten etc). Diet should be 80% hay, 15% leafy greens (introduce these slowly and one per week. Sometimes young rabbits don’t tolerate greens well so it can be better to hold off if very young) and 5% pellets. Depending on the size and age of your bun, up to 1/4 cup of pellets daily is probably ok. If you’d like a better idea of age we can probably help if you post a picture. Gender can be more tricky but if bunny it’s probably easier to find out once he or she matures.
If you’re tight on space some good options that are flexible to different spaces include x-pens and c&c cages. There are galleries of different housing types on the binky bunny habitat page here: https://binkybunny.com/BUNNYINFO/GreatHabitats/tabid/229/Default.aspx that should help give you some ideas
Horizontal space is more important for bunnies than vertical space (it’s better for them to hop along flat ground than up and down small levels). But find something that works for you and your space. Some people use XL dog crates for a home base and then let bunny out into a pen or to free roam the house for a few hours each day.
I suppose the other main thing is litter training. Baby buns can hormonal teenage buns can be difficult to litter train but once they are litter trained it saves a world of mess
Having a hay rack next to/above the litter tray helps, and having litter/bedding only in the litter tray rather than all throughout the cage helps to save confusion. I use wood pellets in my litter tray and fleece blankets as bedding in the rest of the cage.
I’d also suggest that you read up on GI (Gastro Intestinal) Stasis if you haven’t already. It’s one of the most common ailments in buns and can become serious quite quickly. Knowing what to look for can be a life saver
Good diet can usually prevent it but GI stasis is considered a symptom and can occur from a myriad of illness (respiratory infection, tooth problems, gas, pulled muscle etc).
Welcome to the wonderful world of bunny ownership 