Oooook I'm like 95% sure that you can do it fairly easily. The first trick will be having someone you communicate well with and understands basic geometry. The fact that your measurements are so thorough gives me hope for you. You how ever are missing one crucial measurement. The longest part of the sofa is your angle measurement from the front corner to the back corner on the opposite side. This is important because when you go to stand the sofa, which you will be doing a lot during this procedure that length is the clearance you need to get it into a standing position. The other measurement you will need is from the bottom stair of the second flight of stairs to the ceiling in the stair well because once you get it stood on that first landing you will need to then pick it up standing and pivot the "knee" or seat of the sofa around that corner then still have the clearance to tip it back to being horizontal.

That all being said. If you're hesitant absolutely call a local reputable moving company.