Yeah, E2 converts downstream, BUT, right now you're seeing some hyper-converting primarily from your test serum. If you're right at 1,300ng/dl after 6 days, it's much higher at 2 to 3 days, which is when you will see the peak value. Administering an AI at/around 24 hours after injecting would be the best strategy, but consult that with your physician.
Your doctor did a good thing with splitting the dose 2x and reducing your dosage. This will help keep the serum level stable without hitting all those spikes, causing a surge in E2 conversion. Depending on where your free/bio test sits, you might not even need that much, but that's also factoring if you include HCG at some point.
Anyhow, once you find that "zone", your body will be in a better place. Implementing DHEA won't be so bad "IF" you get the test subject under control. Again, it's about balance ... Implementing 25mg or 50mg of DHEA micro can be a wonderful compliment to add balance, but that's permitting you have the test serum under control.
In my case, I do the 2x/week via sub Q, plus HCG admin sub Q. With a little topical DHEA, I can barely keep my E2 in the 20's on a Labcorp 3-70 scale. I keep my serum level in the high 600's, low 700's (give or take), but I am also over 3% on free test (pretty low SHBG).
I add in some of the supplements that were mentioned, run some regular labs, and things aren't too bad. Don't get me wrong, it's a continuous learning curve, and once you think you have it down you get thrown a monkey wrench. Other variables like RBC's & Hematocrit come into play, etc.
However, it's been much more beneficial to me with spreading the focus throughout the endocrine system, as opposed to just completely focusing on some of the primary areas that always get talked about. Trust me, if your adrenals are shot, or your Reverse T3 is elevated out of proportion, more testosterone will just be detrimental. Just my .02 and perspective.