I'm probably not as much help as other people, but I usually work 15 hours a week during semester on top of a 60-70 hour courseload. Last semester, I did this on top of some major extracurricular activities (president of an organization, board member of one of Yale's biggest organizations) and I found that I was very busy indeed and frequently exhausted.
I'd agree with the posters who's spoken about making a checklist. I'd also make sure that you allocate time to do your work on weekends and in those times, do not arrange to go out. For instance, you could decide that Friday nights from 8pm-12am are study times, and that saturday from 9am-5pm is time to study. That would give you a decent amount of time to study. You could also make an additional schedule for weekdays and say that you will work from 7.30pm-9pm each weekday, which isn't much time at all. Doing those study times would give you 18 hours of study time a week, which is definitely enough. Work in an environment without a computer or phone. Leave them somewhere else.
Also, is there any work that you could take to do during your lunch break at work? I generally study while I eat lunch or I go to the library to sort out logistics over email.
This following paragraph is going to sound really harsh, but I really don't think that working 45 hours a week and taking one class is very strenuous - you can definitely accomplish it. Sometimes you've just got to do what you've got to do in order to obtain your final outcome. Even though I often get back to my room exhausted, if I have an assignment due the next day, I stay up until when it's done - be it 1am, 2am, 4am. And there have been many times that I've given up spending time with my boyfriend or friends in order to spend the time studying on weekends. Even if you just dedicate one weekend day entirely to studying, that gives you about 15 hours of studying, which is the bulk of what you'd need. I find that I need weekends to get ahead - without them, I get three hours of sleep per night during the week, which is counterproductive and makes me slower.
For me, a big part of time management isn't finding extra techniques. It's about knowing that I need to get certain things done, and making sure that I get them done. You do need to make sacrifices. You will be exhausted. But you have a goal at the end of all of this, so you need to work to obtain the goal. There aren't really any shortcuts. I'm sorry if this sounds really harsh, but if you do need to work that much, the only other option is for you to persevere when you feel tired and to cut down on the social activities.
Remember that it's just for a year. The sacrifices that you make in the meantime will pay off.