Guidelines are a good starting point, but they won't and don't work for everyone. Your best bet is to feed this back to your Doctors if you're able to contact them easily. If not, you can modify things yourself. So how would you do that?
1) Be very careful.
You clearly know there's a possibility of going low, so be ready to test/treat a Hypo at the slightest sign of trouble. If you have a Libre 2 you can set-up alarms to help you. If you have a Libre 1 and/or a Blood Sugar Testing kit. Don't hesitate to test if something feels off.
2) Modify
If you chop 2 units off your dose and you still go Low. Take 3 off the next time and see what happens.
3) Adjust your standards for "in range"
When I was having the difficulties you described, I would treat 4.9 and below as "Low" and correct with Dextrose Tablets (whilst active). This meant I would catch the Blood Sugar drop before it became a Hypo.
4) Basal Testing
Any time I've had an issue like what you're describing it's been an issue with my Basal Insulin. Try to go without food for the time of day you usually exercise, don't exercise, and monitor your Blood Sugar levels. If the Basal's causing the issue, you'll find your levels are dropping in the absence of Bolus/Food.
With regards to your final question. It's neither here nor there why, as the steps you'd take to resolve the issue would be the same regardless.