We had a much milder situation when baby #2 was born, but my son (who was 34 months at the time) turned pretty vicious toward me (and me only, so no support from others as they figured it was my problem!). I was bruised all over, from the bites especially. Add to that my own sleep-deprivation, soreness, and hormones and we had the perfect storm.
The best little thing that we did was establish 2 15-minute blocks each day, one after breakfast and one right before dinner -- in the morning block I got down on the floor with him and said "What do you want to play?" and we did what he wanted. In the afternoon block we did a sticker craft -- the same craft every day, same time, same place. My husband watched the baby during the evening block, the baby was asleep during the morning one or I called a friend to stop by for 15 minutes. So it was full one-on-one time, one time just to see what he wanted to do (in other words, accepting and loving him just the way he was) and the afternoon was pure structure (babies destroy routine, so this gave a dose of stability to his world).
Not a magic bullet, but it helped at least some. Then throughout the day I'd remind him of those times -- "Your red car sure went fast. I like playing cars with you." Or at night, "What will we play tomorrow?"
I recommend the book "the portable pediatrician." It is really down-to-earth and reminds us what kids need psychologically and developmentally from birth to age 5 -- having one 30-page chapter per stage really helped me cope and was where I got the 15-minute idea.
I see below someone mentioning reading together -- there's a book called "I'm the big brother" (I think it's $4 from amazon... our library has it too) and that was GREAT.
Good luck. Let your older one know he's still the apple of your eye.