Ooh, Tofutsies. I have some of that sitting in a bin. That might be a better option than the Knitpicks...

I also have problems with casting on too tightly. A trick that might work for you on patterns that don't have a toe-up variation is to use a provisional cast on, and then pick it out once you're done with the sock to use a stretchy bind off. I'm a fan of the sewn bind off for this purpose. If you remember to leave a few feet of yarn hanging when you start knitting, you can use that for the bind off and you don't even have an extra end to weave in.