Lynne: what type of environment do you work in?......as in all office, warehouse, combo??......have you talked to your co-workers?? they may actually help you keep on eye on your bike and take care/protect it. Especially if they know that's your only way of getting home.
As for the traffic - I ride like I belong on that rode doggone it.....coz I am after all considered a vehicle. It can be intimidating but believe me, the drivers Know when you're backing down. I don't mean I'm an Aggressive rider, but an Assertive rider. I also - thanks to someone here on the board - try and let the drivers know what I'm doing ie: if there's a right turn lane and I'm going straight, I signal that I'm staying in the straight lane....you'd be surprised how many people will back off to let you move over where you need to be. As for the masher guy - I'm with you, I'da just let him go. If it happens again you might try stiking up a conversation with him, ask him if he finds it easier to start in such a high gear!!
I'm sorry to hear about the locker - you may have to leave a duffle bag under your desk to keep you biking clothes in.....or talk to the other ladies and see if they'd mind if you left them in the restroom.....heck - ya might inspire some other ladies to ride too! Someone here I think said they had a friend who laid out all her bikie gear under her desk to dry out until time to go home.
No matter what, you're already doing more than most people even dream of, keep up the good work and it will work out for you!