Estrogen rebound will be the biggest. Your lowering estrogen to a point that is below normal. Now usually the body will compensate in the long run when the dosage is discontinued. Thats why tests need to be contnued for months. As you see in the chart above, recovery from a suppressed state can take much longer and test levels can drop drastically when use is discontinued. THe inverse is true also. Testosterone levels usually go above normal then slowly fall back to normal after a cycle. Estrogen will do the same if you suppress it enough.
As for your bridge theory, I don't understand what your point is. You not feeling well is a result of an imbalance in hormones (probably) and I don't see how Letro can help this. It won't raise testosterone until LH pulses and the testes recover first, and thats what Nolva does better than any anti-e. Your basically adding another anti-e that won't help much, if at all and may cause esstrogen levels to peak much higher wehn PCT is complete. I would save it for another cycle (maybe 1,4 diol) but thats your choice.
THe problem with your lab test also is that its not showing true recovery. Its showing the effects of the drugs being used. As you can see in that study that can give you a false sense of recovery because as soon as the treatment was stopped, test levels fell back to below normal. Now of course that won't happen with everyone but its easily a possibility. What you need is a baseline fomr when no PCT is used to determine what is natually occiring and what is drug induced. Luckily there have been many studies already conducted on this subject that are available. The general consensus is that LH returns fairly quickly, wth or without SERMS, but the response of the testes is better when SERMS are used (best when HCG is used). Also testosterone levels usually peak higher than normal then slowly fall back down when succesfful PCT is done. So for your lab results to be conclusive as I stated earlier, it needs to be followed out for a much longer peroid of time. YOu will basically report what is already known, that Nolva helps you recover. I say use that lab of yours for other issues. If you need suggestions I have a million of them, especially with cortisol and SHBG post cycle!
But its up to you...I think for a thorough and complete test on PCT, this needs to be done for a minimum fo 3 months. And there really is no way of distinguishing what each is doing. Your profile would probably look similar to the study above with much less circulating estrogen.