I would try feeding from just one breast per feeding and doing breast compressions to help get you LO more hindmilk towards the end of a feed to see if that stops the green poops. If you LO doesn't have a bright red ring around his anus and there isn't a history of allergies in the family I wouldn't bother with trying an elimination diet at this point.
If you still have green poops after 3-4 days, try block feeding offering only one breast for two hours then offering only the other for the next two hours.
As for forceful letdowns they tend to work themselves out as the baby gets older. Try a cross-cradle hold or a football hold while reclining back and that will help your baby slow the flow. However by 3-4 months the baby might get fussy because the milk doesn't come fast for the entire feed.
http://www.kellymom.com/newman/15breast_compression.html
http://www.kellymom.com/bf/supply/foremilk-hindmilk.html