You don't need visa to enter US if you travel before 2,3 months of your visa expiry. But to be in safe side you need employment letter  and most importantly new approval I797 in port of entry.

your wife need to apply visa and if all docs are fine she should get it quickly.

If embassy know that you are also in Nepal when your wife is filing visa, they will ask you to file visa too so that both password will have visa with same employer and expiry date matching with I797.