Low dose T3 can actually exhibit anabolic action congruent with its metabolic stimulatory effect. Colorie restriction, especially if your leaning out quite a bit, will tend to lower endogenous T3. If I were in your position, I'd consider running 12.5 mics a day. Use too much, especially without AAS, and not only will you have to worry about a catabolic effect, but your muscles will be flat as hell via glycogen depletion.
If you're really tempted, I wouldn't excede a max of 25 mics a day. If I were to hit the 25 mics, I'd do so in a typical T3 pyramid scheme - week 1 = 2.5 mcg, week 2 = 25 mcg, week 3 = 12.5 mcg.
Yes, the T3 at either of these doses, especially combined with clen, will give you results in less than 3 weeks.