Hard to pin down whats going on but there are a few possible at play that might be worth considering.
There is a 'honeymoon' period (for you new types
) where the beta cells are still working, you might still have a bit of that going on - from research over the years most of us still have a few beta cells doing stuff, but they tend to get less and less over time.
What possibly caused your T1 is the virus was identified by your immune system, and this identification also flagged your beta-cells as the same virus, and so your immune system went for them too (might be wrong there as not read up on this in a while, but I think thats how it can work).
Worth bearing in mind FIASP has a DIA (Duration of Insulin Action) of around 9 hours in most people when you're pumping and using HCL - so more is active than you think (I am jealous of how little you need tho
).
For your return to normal BG after a meal - thats what you should expect on an ultrafast insulin - they kick in at about 15 minutes and peak at around 55 - as I say some is still active at 9hrs (though it tails off) have a look here:
The values that we use for DIA in pumps and bolus wizards is wrong. Here's why and what you can do about it.
Sounds like you still have an partially active pancreas - this might get worse over time, or you might be able to find ways to work with that.