1) If you think he really would beat you up just leave them to it, no point in risking your neck! You don't need petty customers like that. But if possible go back and apologise and ask what problem there was with the job you did, and try and rectify it. Often this disarms people. Just be professional, keep calm...I've had irate customers like that that have been out of hand, unreasonable and have cancelled but have asked me to resume at a later date after calming down. Sometimes they just don't get wfp to start with.
2) I would have tried to keep calm, asked for half the money, if I'd done half the job, and if he refused just accept the money offered and just leave it at that. Fair enough. (and keep well clear in future!) Some customers are often that stupid and don't read the info sheet you give em.
3) I would have done what you did, maybe not clean the whole house if it didn't need doing, just wiped the drips etc. You can point out that marks are on the inside (or even inbetween panes) if they are, and people are often apologetic because they don't always realize marks can be on the inside! I would be wary of her in the future though and make sure you get paid before you go back again.