First, great progress! You have a great physique!!
Now a few thoughts:
This is something that weighs on me as well. If we are talking about "diabetic burnout", this seems to come in waves to me and was much worse in the beginning after dx. Particularly after periods of really tight control. Nowadays it hardly comes up as the habits have become so engrained. I know exactly what you mean though when you say you can't remeber what it was like before! I used to frequent the pizza buffet before dx, but now I won't even touch a slice! The lack of freedom brings me down a bit. It could be ironically argued (and rightly so) that I am much healthier now than before I had diabetes. Nowadays I do not even crave pizza, but it would be nice if the option was even on the table without the consequences!
If we talk about the idea of more insulin = decreased longevity, I have run across this idea before as well. What helps me is to remember a few things. For one, and this sucks, but we have a serious disease and have to supplement with insulin to live, so not having it means a much more immediate death. Thoughts on longevity take a back seat to that. This idea really bugs the crap out of me as I take a great deal of pride (before dx and even more so now) in being healthier and performing better than your average human. Being held back, at no fault of my own, does not sit well with me. Hence the drive to push in the gym and in the kitchen. Having said that, I would bet that study was done on type 2 diabetics who use an HUGE amount of insulin in comparison to us. As Bluecollartr8n once said to me when discussing the subject, he thinks the idea would be to use as much insulin as is necessary to get the job done and no more. I would tend to agree.
In my run in with post dx "bulking" I have come out on the other end thinking leanness and insulin sensitivity are much more important to me than shear size. The nature of what we do almost mandates that we seek size and strength (in addition to other physical qualities), and I will continue to have those things on my radar. I just have to prioritize them differently. When sensitivity started tanking so bad, it scared me TBH.
Also, I think it important to remember when talking about insulin and it's dangers, that even Normos need it to live and there has been nothing, as far as I know, saying that the artificial stuff we use is dangerous in and of itself. I would wager as trained individuals who eat well that we have to take less than most Normos make for themselves, and if not, certainly it is about the same amount.
I watch The Walking Dead and have always been a zombie fanatic of sorts, so after dx, I got curious as to how long I could live if the shit hit the fan and society fell apart and I ran out of insulin. My old endo didn't have a clue, but let me borrow a book that detailed the creation of insulin by Banting way back in the 20's (surprising fact: after I read it and tried to discuss it with her, I find out that she had not, in fact, ever read the thing...). In the early chapters of the book it went in to how diabetes was treated before insulin was created, and the only thing they had that seemed to work at all was a starvation diet. They would test the patient for sugar in their urine and basically reduce calories until the body stopped excreting it. Sometimes it got as low as 4-500 calories a day. This of course was really just prolonging the inevitable and they all died in the end, but some managed to live a surprisingly long time. Maybe because they still made a bit of insulin themselves. Either way, the point is (other than in a zombie apocalypse hoard insulin and find a way to refrigerate it) that we need it to live regardless if taking it will kill us earlier than Normos. I know that that is not a lesson that you need at all, it just always helps me to point it out to myself when feeling burned out. It could always be worse...
This is a good topic for discussion and I wish I had more to say, but I would just echo what you have said. Intervals are my cardio of choice and in my experience also intervals are similar to weights in that they increase IS. SS cardio, while I tend to loathe it is sometimes a necessary evil though. the difficulty I have with it is that it lowers BS, so finding a way to do it to actually burn fat is difficult. I mean, if you hop on the treadmill (or go for a walk) for 20-30 minutes or whatever, you are going to have to take some glucose or something when you start to drop. Adding calories seems counterproductive when trying to burn calories! A possible solution would be to use it post meal ans give less insulin before the meal. There are extra carbs/calories in the system and by being physical, you enhance the ability of the insulin you do have to do it's job. The net result is less overall insulin is used and there is no need to ingest more glucose when going low during cardio . For example, let's say you normally take 5 units and 50g of carbs at dinner and go sit on the couch. All is good in a few hours. Now, let's say you take only 3 units (or even 2) and go for a walk or something. The extra carbs you ate will still be taken care of by the insulin because you are being active and you won't have to worry about going high. you would have eaten the calories anyway, but didn't have to add more just for cardio. I hope that makes sense.. Another way may be to weight train with less insulin in the system as it can tend to raise BS, and do cardio afterwards to lower it. Less overall insulin is used for this as well and no extra cals neded. This of course requires more time in the gym. You would have to train in a way to raise the BS (more intensity and such), and have the time to do enough cardio to lower it.
IMO intervals are the way to go most of the time. SS cardio has it's place though and should still be done to some extent. I have found that my BS doesn't really begin to drop until around 15-20 minutes in, so used as a warmup/cool down or something has little effect. Faster, higher density weight training and supersets are always a good thing too.
I have enjoyed discussing this stuff as there are few I have been able to talk about it with. I hope I do not come across as a Know-it-all though, as there are a great many things I am still figuring out too!