Hi again, good questions, I'm not sure about ketones but I would imagine that it will be similar to why you crash when doing exercise, especially if it makes you sweat.
The reason is called a liver dump, of glucagon/glucose which boosts the amount of glucose in the blood.
This is similar to eating carbs.
Because you use your energy levels, the body/brain needs more glucose to keep your energy levels up so that you can do the exercise. This is a normal part of life.
As you know when the liver dump happens, you need insulin to get that energy, you get too much, which makes you crash. The trigger is so similar to eating carbs.
I used to do a lot of walking, this helps all round with your health. Being busy walking up and down stairs and so on, is enough to help with your control. Swimming, gentle aerobic exercise as long as it's not too much.
You are going through a life-long change in your life, where you need to think about how you approach the future. Knowledge is key and the more you know about how your body works.
We both have rare conditions, our metabolism is weird compared to the other 99.9999% of the population. There has been a lack of research on these types of conditions. The specialists know about them, but have probably never had a case.
Most of these doctors have not gone through the long list of symptoms, hypos or the damage it does to our health.
That is why, we need to find our own way, and do what actually works for us.
I believe it took me two weeks (ish) in the summer to get back into ketosis.
The only other time was when for some reason, an apple spiked me high, and it wasn't a bad situation because I nursed myself back into normal levels, by not eating too much and low carb. I was fine the next day.
The first time, I went into Keto, was after my fasting test, and I just carried on with being in ketosis, the transition had already happened within the fasting. And I didn't get the carb flu!
I do think that there isn't any standard time to go into ketosis, It all depends on the individual.
Stay safe