I get what you are saying mate, have you a friendly watchsmith that you can go to to get advice and guidance? If you have pop in to see him /her and ask them to help you put that crystal back in. I know you might think this is not teaching you how to do it yourself but believe me I have used mine for some really simple stuff that was bugging me, and they enjoy passing on their knowledge.
Them claw lifters also need to be used with the clamp to ensure the jaws all stay the same height on the crystal, I sometimes have great success with these and at others ive cracked crystals left right and centre using them.