There is no IDEAL level for everyone. We all vary in our response, sensitivity. My levels are around 1,000-4,000 pg/ml.
The more important question to ask is do you feel good? is feminization progressing well? Higher levels aren't necessarily associated with increased health risks, some doctors ignore this. Risk is associated more with the type of estrogen and route of administration. I take bio-identical estradiol non-orally, as you are. My blood test results are fine. Studies have shown transdermal estradiol to be safe in men with prostate cancer (49-91 yrs old) despite levels being higher than 500 pg/ml.