Aww, I totally understand your fears as I've had them myself - so you're not alone in this. When you love a kiddo SO much, it can be very hard to feel peaceful about having anything done to them that involves even the slightest risk.
Leg lifting seems to be inherent to some dogs, no matter if fixed or not -- so it's tough to say if neutering will help w/ this problems. It does help some dogs, others it just doesn't change it. So, can't predict that one with any surety.
As far as anesthesia...again, I totally understand your fears and have been there. But I can assure you it's VERY very safe and complications are so incredibly rare! You ALWAYS want to do pre-surg bloodwork bc you want to make sure general health is fine and that the liver / kidney / blood cells , etc are within normal limits. This gives that extra assurance that your kiddo will do fine.
As far as neutering in general -- it's a personal choice. My preference would be to keep their natural and needed hormones intact bc hormones play such vital roles in our bodies. However, there are benefits to fixing pets - as I'm sure you're already aware. All 3 of my kiddos are fixed.
This is a thread you may want to read:
http://www.yorkietalk.com/forums/gen...n-if-ever.html
The bottom line is...try your best to put your fears aside so that you can make a good / rational decision -- and so that you can assure yourself that as long as your kiddo is healthy, everything should go wonderfully.