Keto keeps my BG high, low carb has dropped it. Why?

I need some help from people way more knowledgeable on the subject than I am.

I've recently been diagnosed with diabetes (age 40) after a rapid and sudden onset of a 11kg weight loss between Nov-Dec w/o trying (had been eating SAD from about March to Dec last year after 8 years on Keto), god awful thirst, dry mouth from hell, yeast infections, keto pee/breath when I was NOT close to doing keto, and of course vision going completely blurry to seal the deal.

My starting fasted BG was 18.9 with an A1C of 114. I got it down to about 15 just by going back on keto and I adapted back in a few weeks (I noticed the longer you're on it, the faster you fat adapt again and I'd only been off a few months after doing it 8 years). After arguing with everyone that I could be LADA I got put on Lantus and it started going down. I'm now on 16u at night but have never had a fasting BG below 8 even though by noon or 1 I'm in the 7s and hitting the 6s after exercise despite being under 25g of carbs and under 15 on most days so far.

I had a call with my internist Monday and asked to try some fast acting insulin and she refused saying I don't need it as type 2 (I did wear her down and get the tests for type, but we're waiting for GAD and the other antibodies to come back still). She also won't prescribe a CGM saying I don't need it as a T2 so I've no idea why I'm waking up with such a high fasting BG after eating maybe 25 net carbs in a day. And don't worry, I've tried lowering protein, stop eating before 6 and 7, eating only fat for dinner (disgusting and didn't work), etc.

So I got pissed and told her if I'm a T2 I'll just follow the T2 dietary guidelines and up my carbs from 20ish to 150 max.

Breakfast gave me a pretty bad spike of 8 to 13.5 (oats and skim milk), but then dropped me to 5.5. Lunch was keto so only had 1 carb but I had strawberries as a snack. Spiked me from 5.5 to 8 then back to 5.5.

Question, what in gods name is my body doing? Why is 150 (67 from yesterday) better than 20? I'm confused. Someone in a LADA group said I could be producing some insulin on my own still and that combined with the lantus is putting me back in normal, for now (my c peptide is 1.4 and I think the scale is .9 to 4... my fasting BG for that day was 9.5ish).

TIA!

TL:DR when I eat under 25 net carbs my BG stays 1-3 points above normal and refuses to come down. Between 25-150 not only did fasting drop to normal, it's staying normal outside of spikes of 5-8 points or so.