The thing is, if you tap a big dude a couple times of course he's going to start being overly aggressive so expect it. Nothing calms down those guys like a nice over hook to falling/flying armbar. Either that or pull guard and get to a deeeeeep ass mission control/crackhead control and work the basic path. That or get to the back via armdrag or whatever floats your boat. Those are fights id rather be fighting than his weight stuck ontop of my smaller/weaker frame. Pick and choose your fights and try not to keep getting stuck in the same places.