hmmm, that's hard.
Well I had similar problems in thief 2. - It could be too hard (compared to T1, DX, SS)
Yep, the turrets you mention are nasty. On one tour through the game I had to reload an earlier part to get past them. Hacking the security is by far the easiest way here.
If you use too many nanites in respawning, think about reloading more often. Hacking, shopping, modifying need also nanites.
Don't give up! Eat some chips, drink something and stay alive! The Rickenbacher needs you!!!