I just got done posting some good info
here regarding stasis-prone bunnies. Your situation differs from that one, as the other rabbit had gas issues and you've got hairball issues, but a lot of the basic info is the same. Correction, I *thought* when I posted that it was gas, but an update from the owner indicates it may also have been a hairball... regardless, I listed some good things to keep handy for stasis-prone bunns
.
Anyway, the specifics for your situation... first of all, when you say "2 cups total of carrots, green beans and Romaine"... Romaine is a leafy green veggie and two cups of that is GREAT... but carrots/green beans are both non-leafy greens and should be limited to no more than 1 tbsp per 2 lbs body weight combined.
More great diet info can be found here. 1/3 c pellets is actually a little high for a 5 lb rabbit (and for a purebred lop, even one lacking the dwarf gene, he's just a wee bit on the heavy side (4-4.5 lbs is more where he should be).
For a Holland Lop, I recommend (per day):
~ 1/8-1/4 c pellets
~ 2 tsp fruit/treats (max)
~ 2 tbsp non-leafy greens (or edible flowers)(max)
~ about 2 cups (packed) of leafy green veggies
and, of course, unlimited grass hay
You need to brush or groom him thoroughly on a regular basis, especially during a molt. Personally, I love the Furminator, but any non-wire-tipped pet brush or comb will work. You can also dampen your hands with water, run them over him, rinse and repeat. A little more tedious than the Furminator but has the added perks of being both effective and free.
During bouts of stasis/decreased appetite where he is eating but eating less and/or pooping less, cut out or dramatically reduce both pellets and leafy greens. Don't feed non-leafy greens, fruit or treats at all. Push hay and water. The fiber in hay and moisture from water will help the hairball break up and make its way out of his system. If he stops eating and/or pooping entirely, it's vet time.