To be successful in aviation these days you really have to be driven and passionate about it. I don't want to sound mean, but if you can't pass a remedial math class then you have no business flying hundreds of people around at a time. If you really want it you will find a way, and ignore people who say you can't, but it seems like you want a guarantee and no one here will give you that. To answer your question in general, Part 141 schools usually take less time to get ratings, but have a stricter curriculum that they have to stick to.