I'm sure other people can offer better advice on this. I only have one thing I do here. ( I am assuming you had control of your opponents right leg and he was attacking your left arm?) If so, the first thing I do is damage control on my left arm (the arm he is attacking). Ideally I can grap my hand or wrist to keep my forearem close to my chest. If I can't get that, I will grap by bicep like I was doing a RNC. After that, I give up my lockdown. Because my opponent is putting a lot of weight on my arm, his legs and hips are relatively light. Once my lockdown is released, I straighten my legs and bring my right leg underneath his right leg so I have conceded side control (basically, I am sliding my right leg under his leg so it is no longer inbetween his legs). At that point, I sit up and turn to my left side at the same time. Because my hips are so closed to his hips, and his base is far forward attacking my arm, I have a easy time sweeping him, and once I'm on top, I have an easy time preventing him from america-ing me. For me the overall motion is similar to the transition from quarter guard to the dog fight, or maybe more similar to the motion when you do the hip bump sweep from the closed guard. I am sitting up and then rotating my body as if I wanted to go belly down, that has the effect of bumping my opponent off of me and I land on top. I hope this makes sense, I can try to explain it better...
for the gi game, I only think there could be a bow/arrow type choke if he went twister pass (i.e. a gi substitute for arm tri angle from the bottom