The delivery was induced at 33 weeks gestation because I had extremely high levels of protein in my 24 hour urines. At 4 weeks postpartum, there was still protein and microalbumin in my urine. My obstetrician said the protein would gradually disappear and not to worry about it. My endocrinologist said the microalbumin was an early indicator of kidney damage and I should begin taking ACE inhibitors to slow the progression of the damage. You have several questions which I will answer in the order you wrote them.
Albumin is a component of the all the protein excreted in the urine.
Although the presence of albumin in the urine may reverse, it does represent a progression of renal disease due to diabetes. Therefore, the ACE inhibitor may be of benefit in delaying future renal impairment. The fact that you are now having albumin in your urine is probably mostly due to your diabetes and less so to the preeclampsia. Usually, the protein in urine due to preeclampsia reverses in a few days. Delivering the baby any earlier probably would not have changed the outcome for your kidneys.