Don't give up Mate, it happens to every modder at some point.
Once early on in Sancre Tor, I spent couple hours carefully hand placing dozens of floor and ceiling tiles in the parts of Sancre Tor's interior where there is no floor or ceiling. Then I tapped the F key to drop a piece, but it was too far up and the CS CTD. I just stared at the screen, stunned, at first couldn't even believe it was happening. Then I realized I hadn't saved and would have to start that whole project over again. And there have been at least a half dozen other examples, too painful to rehash!!!
I know exactly how you feel and you have my sympathies. But, it's a risk we assume when using the CS; it is a crashy beast by nature. The best advice is to pick yourself up, dust yourself off, and start again. Save often, and always before making any major changes you haven't tried before. If your PC can handle it the CS also has an auto-save feature that can save every few minutes in case you are forgetful!
You can also search the wiki for examples of things that cause CTD in the CS so you know what moves to avoid (like hitting the F key to drop an object from too high!)
I don't think I'll lock this thread just yet, there may still be work for you to do in Aleswell!