Twice a week DC fashion? Is that every other week?
Also, you need to rotate between 3 biceps exercises in the DC format. Seated dumbbell curls are fine, but also throw in some concentration curls and possibly Zottman curls (not the best biceps exercise in my opinion, but if you have a real lack of equipment they'll at least hit your biceps and build some brachialis and brachioradialis as well).
You should also read Dante's post titled "You guys on the 2 day split better smarten up" over at IM. Basically in it he describes in a simplified format how to choose your exercises if you want to bring up "weak" body parts.
Finally, if you have hit a plateau you might want to take a deloading/off week or two to allow your body to fully recover. If after a few weeks of going back at it you still can't get past this plateau, then perhaps you should check your diet. If all else fails, then maybe think about trying some "plateau busting" techniques.
Oh, and yeah, joining a gym will certainly give you a lot more options in terms of exercise selection.