This is a good start to the story (not a crossover I'm very familiar with, but it works well with the Buffy verse) and I'm pretty sure you have something promising here.

If I can make a constructive suggestion, however, it's that you're probably being too much of a perfectionist. I've started reading the story three or four times and haven't seen anything wrong with any of the chapters you've taken down. If you let the story grow, then you're more likely to receive reviews and a growing following, but right now anyone reading it probably expects you to remove the chapter again and so won't take the time to review.