Ok, Your advice is good, but...
1) how do I do that? The chain is stock, I imagine surly put the optimal chain on it, if it isn't, how do I tell?
2) How do I do that and define optimal? really dumb the explanation down for me cause I'm ham-handed and tend to break little mechanical doodads.
3)rear derailleur seems adjusted properly as it shifts well and doesn't over shift. Front derailleur is on friction shift, but I don't think the limits are the issue, the chain comes off the bottom of the chainring, but I'll look at that anyway.
4)will do.
5) I do try to do this, in fact I do these things all softly enough that my u-lock doesn't fly out of my back pocket. Yet the chain does pop off. it even pops off if I hop off the bike then quickly lift the bike up and put it down against a wall. It's beginning to piss me off.