3 weeks is not even close to long enough to wait before attempting an assist feed ... you'll end up doing more harm than good.
Try a live hopper mouse in the cage with some crumpled up newspaper over night ... and stop messing with him.
Here's a link to an article that I wrote for my website a few years ago ... it might help as well.
http://www.8ballpythons.com/journal/...ingseating.htm
Good luck ... and remember, assist feeding is a last resort ... not something that should be attempted because you don't feel like waiting any longer.
Hope this helps.
-adam