Which is best for g a d . buspar (buspirone) or remeron and which has the least side effects. thanks?

Too many!: You already take drugs appropriate for GAD and either of the ones you wish to add are VERY risky in combination w/ the Lexapro (escitalopram). Neither is advised. Tere are also less severe warnings about their interaction w/ your diazepam. Don't expect everything to be done by pills. There is strong and massive research that shows these are all more effective in combo w/ CBT therapy. You need to get involved!