An instructor has to learn just like you.
Unfortunately the present systems does not encourage career instructors who have long and colourful logbooks so many having surprisingly few hours to their credit.
Whilst I am not an instructor, I do a reasonable amount of right seat flying. There are times during any flight when you realise that if the "student" makes a real mess of things recovering the situation is going to be interesting - fortunately such times are relatively few, and have a great deal to do with how close the ground is! In these situations there is a fine balance between how far you let the "student" go and when you take over. Ideally you want the student to go as far as is reasonable.
Of course you dont say how much instructing your man has done and perhaps there are other reasons for his anxiety.
A more informative answer might be possible if you gave some examples and described which excercises you are doing.
However to hopefully put your mind at rest there is very little you could do that will put you or him at real risk. There are a number of excercises where the instructor will be well aware that there is a risk of your getting the aircraft into a situation outside its normal envelope and he will be wary during these excercises and ready to take over before the situation becomes dangerous. Maybe you are at this stage?
Of course having clearly briefed you on the touch drills for a engine failure if you actually turn off the fuel the engine will stop and it jsut might not start again! The instructor should do a reasonable job of the FL but he is going to earn his keep.