I would suggest a second (and/or third) light...front and rear. Stuff happens. Cords get damaged, mounts fail, batteries drain, lights get broken in crashes, etc. Having multiple lights reduces the chances of a single failure leaving you riding in the dark. And battery headlights are so cheap now that you won't break the bank with multiple lamps and batteries.

I also find a helmet mounted light to be indispensable. You can direct the light where you need it, like corners. The motion of the helmet light is also eye catching to drivers without the annoying flashing. Be careful with a helmet light, however. You don't want to look people in the eyes since the light goes where your head is pointed. You can use it to get the attention of drivers how may pull out from stopsigns on you but use it that way sparingly.

I would also investigate alternative routes. 45 to 50 mph traffic isn't fun during the day and is much less fun during the night. I bet you can find something that parallels the route on a quieter street.