As crazy as it sounds - you are likely to have a faster result downward by LOWERING your dose from 100 mg currently to 70 mg or even 50 mg. I'll explain.
Dasatinib (sprycel) is a "threshold" drug. Its half life in the blood is only 5 hours, so it works right away or not at all. It also impacts our normal cells during that same time (not just side effects) in that it causes suppression of our immune system. Adding more sprycel in the mistaken belief that more is better and leads to deeper response has been proven false (for dasatinib). The key is to find the correct dose for you. If 100 mg is getting you to 0.05-.08 (which, by the way is statistically zero difference - you simply have plateaued at that level), then lowering your dose to 70 or even 50 mg could very well take the strait jacket off your immune system while also attacking CML. It's not the dose, it's the threshold. That threshold dose is different for everyone. The new starting dose for sprycel is emerging to be 50 mg ! because of the success rate and the much lower side effects (pleural effusion).
I take only 20 mg sprycel and I am "undetected". It wasn't until my doctor lowered my dose that my PCR plummeted. You want your drug and your immune system to fight CML. Too much drug hampers your immune system, so the idea is to find the sweet spot where both drug and immune system is fighting CML. Some patients need more drug to cross over their threshold. For them 140 mg gives the same result as 70 does for someone else. We're all different.
Given your current PCR (and I assume you have few blast cells), you can experiment with lower dose for one cycle (6 - 12 weeks) and see how it works. You can always increase your dose. Or just stay where you are and it's quite likely you will break through your plateau and resume your drop.
Show your doctor the paper above - chances are he has not read it. Ask him how many patients he has and at what dose. Inform him you know of patients taking only 20 mg and have had incredible response. In fact, you should tell him you know patients who only after LOWERING their dose did their response increase. Most patients had to lower their dose due to side effects and then it was observed that their response improved. That's how they found out this inverse correlation. It's not true for everyone - so it is an experiment to try.
All the best.