I'd say no, I think some people get a bit paranoid about taking t3 without gear whilst cutting.
I wouldn't say the ratio between fat/muscle loss isn't much if any different from taking t3/no gear and no t3/no gear - if you loose fat quicker then of course you will loose muscle quicker.
I would think so. T3 is 4-5 times stronger than t4. My doc has me on around 100mcg t4 ED. So that would only equate to about 20-25mcg t3. To much and you will loose muscle and feel like crap. She had me at around 150mcg and I was loosing muscle. I stay at 100-125mcg now You will end up looking like a smaller version of what you already look like because the fat/muscle ratio will remain the same if your burning muscle also. I'm on HRT so I take appox 140mg test a week also. I can maybe push 125-150mcg t4 with it, but no more as I will get diminishing returns.
Yes. * is replacement therapy amount. As you diet the tendency is to decrease TSH and thyroid levels. If you replace back to normal then you will continue without too many adverse effects - including muscle tissue catabolism.