First of all, you did NOT kill your babies. Please do not ever, ever say that. Your pregnancies were much-wanted.
Second, it is sad that your RE seems to be so off on this, and I'm sorry that you've had to go through what you've gone through. I'm very sorry for your losses. Unfortunately you can't get those two years back and nothing your RE can say or do now will rewind the time.
But--and this is a big 'but'--you do not know whether those treatments would have prevented your losses or gotten you pregnant. Unfortunately there is no magic with an ART cycle. Women who are getting proper treatment have failed cycles and losses all the time, sadly. You're obviously correct that there ARE things that can be done, but you might have had the losses and the failed cycles even with treatment.
I say this only so that you do not point the finger at yourself or play the horrible "what if" game. I have tortured myself with my loss, going over every day in minute detail to see if I did something wrong. Did I eat something that caused an m/c? Was I too stressed? What if I had done this? What if I had done that? Ultimately, I will never know "what if." And I did nothing to intentionally cause a miscarriage. So I am not to blame. And neither are you.