1. Is it bad that i’ve never had him fixed? I wouldnt want health or frustration problems down the line.
It is emotionally and physically better for a rabbit to be fixed. This website lists reasons why: http://www.veterinarypartner.com/Content.plx?P=A&A=489
2. I never even thought about buying a second, but is it bad that he isn’t around other rabbits? Does he feel lonely?
Rabbits are very happy with a friend, but if you spend time with him frequently on his level, then it is not necessary.
3. Until now I’ve been buying him some food at the local petsmart/petco but have read up and am immediately switching to Oxbow.
Not sure the exact question here, but food with seeds, colored bits, or nuts should never be fed to rabbits. When switching to Oxbow make sure to make the switch gradual, there are directions on the back of the bag to help guide you.
4. How often should he be fed veggies/fruit/treats and how much? I give them to him very sparingly but I’ve seen so many different people say all kinds of things. But really what is best for MY size rabbit?
Rabbits don’t need fruit or treats, however a rabbit should have a cup of vegetables per four pounds of body weight, hay 24/7, and a 1/8 cup of pellets per found pouns of body weight. Since you haven’t been feeding your rabbit many vegetables it is best to start with just one type of dark leafy green (NO ICEBERG) such as Romaine letuce or other lettuce mixes. Over time you can add other vegetables one at a time and gradually.

I hope this helped

Just so lomg as he is in good health, not obese, and neutered by a rabbit savvy vet; I have seen five year old rabbits neutered with no complications.