Hi, a fellow type 1 diabetic here! It's great to see a thread where this stuff is discussed since the info from doctors and other sources is usualy so general and aimed for people who don't have their diets/exercise in good check.
I can echo a lot of what Greenchikin has said and I thought I'd offer my own experiences (although your science discussions might be too out of reach for me).
So, I'm now 24 years old and was diagnosed a year ago. The onset was gradual increase of symptoms for about 2-3 months, then couple of days of really bad high sugar symptoms, after which I went to the doctor, got the diagnosis and what not. At the time I weighed about 90+ kg (I'm 173 cm/5 foot 7 tall)
In the beginning I used about 8-15 units of Lantus a night, no morning Lantus iirc. Daytime was controlled with NovoRapid meal insulin, usually around 1 unit/10 grams of carbs. I only counted carbs for insulin (and still do).
Couple of months in, at the beginning of summer, I had gotten fatter (up to 95 kg) due to laziness in diet, not diabetes. Then I got tired of that and took up a stricter diet. Now year later I'm 84 kg, about 8-10% less bodyfat and feel great (I guess I'm around 14-16% bf now). I use only about 4 units of Lantus in the evenings I haven't trained, and zero when I have. I require 1 unit of meal insulin for every 20-30 grams of carbs, but after training it's close to 1:50 ratio.
Some things I've figured out along the way (obvisously this is just one dude talking, I'm not claiming any universality. It's a relatively practical list, so don't expect any fancy theorizing)
-my "honey moon" seems to be lasting for a really long time, going on for the 10th month. I suppose there's no way of knowing if/when the decline starts, but currently diabetes is pretty easy
-for the past 6-8 months my average blood sugar has been around 5-6 mmol/l (here in Finland we use those units, I'm not familiar with your system). The standard good range is 4-7, 4 being the hypo threshold, so I'm doing really well. I measure often, and I probably go below 4 once a month and over 7 once or twice a week. No bad hypos, since my insulin amounts are so small.
-even though there has been some talk about the GI of carbs not being accurate or important, following the numbers has worked really well for me. For example lentils and beans are great on non-training days, I usually need really little if any insulin for 40-60 grams of carbs coming from them
-starchy high GI carbs are trickier, potatoes being the worst, they spike me as badly as candy or pastries. I do eat a lot of rice though, and that requires the 1:30 ratio.
-fats work "as planned": they slow down digestion, thus lowering my insulin need, but this effect seems to be more pronounced with low GI carbs, up to the point where taking any insulin just lowers my sugar.
-what Greenchikin said about training is very true: steady state means just acute increase in the efficacy of the current insulin, no effects afterwards. Medium volume and medium intensity is great: it doesn't lower my sugars terribly, and afterwards carbs are just sucked in like crazy. High intensity, low volume is better for sensitivity than steady state afterwards, but not terribly good.
-I did a meet on Dec. totaling 535 kg. The rest before the meet week was full of studying stress and bad sleep: this f's my sugars like crazy. Stress makes sugar go high and even few nights of 6 hours of sleep make my sensitivity go down the drain. Usually it's about 50% increase in meal insulin when that happens. The meet day itself was wacky, with a very carb moderate breakfast my sugars went over 10 mmol/l and I needed to use 3-4 units of Novo to get that i order. So sleep and stress are huge factors.
-I occasionally drink alcohol. Those nights are like training days, meaning no Lantus, because drinking lowers sugars afterwards. Also I can eat moderate meals pretty freely, since the alcohol lowers the sugars for me also during. I also try to stay on the higher side of the good sugar range (6-7), just to be safe. For me normal amount of alcohol is about 3-6 drinks.
-Currently I follow 5/3/1 full body with lot's of bodyweight assistance and intervals done afterwards. I haven't done intervals or cardio before this consistently, and now I feel great, but I must say that I don't see a difference in insulin sensitivity etc. compared to just only lifting weights with moderate volume/intensity.
-Before training I eat something like oatmeal and cottage cheese with some PB, sometimes a meal with rice and meat. For the former I don't inject anything and there's is a very moderate rise in blood sugar. For the latter I inject about 1:50, but sometimes I need some a couple of glucose tablets right before starting training (I walk 1km to the gym, which lowers the peak of the pre-workout meal anyways).
-My normal meals are around 500-700 calories with about 30-60 grams of protein coming from dairy, meat, fish (I eat quite a bit of pollock and baltic herring), chicken and eggs. Carbs are usually 30-70 grams form rice, oatmeal, sweet potato (much lower GI than normal potato), chick peas, different kinds of beans and some rye bread here and there. Fats are around 10-30 gramsn: olive oil, avocado, coconut oil and fats from the protein sources. I get about 150-180 grams of protein, 200-250 grams of carbs totaling around 2600-700 cal right now, with the rest coming from fats.
I hope you can get something out of this, even though it seems that you both are dealing with a way more severe situation than I am.