@gianmarco, I'll bet there are consumption adjustments you can make so your body behaves more efficiently, but I also think it's important to remember that these conditions are just harder on us bigger people. Don't set the bar at the levels of our smaller friends have established. Just try to improve future you in comparison to current you. I've figured out what works for me, but am ignorant to anything beyond it. All I'll say is listen to their suggestions. I went through something similar a few years ago and made adjustments based on the peanut gallery's feedback until I consistently got through my runs without incident.
But there may be more that you can do beyond just intake. And I realize I'm a broken record at this point about recovery running, but I wonder if your easy runs were ran easier if it would have a positive influence on the amount of fluids necessary for your more demanding workouts. I think consistently running hot has a cumulative effect that gets exacerbated in these conditions. If I recall you've always been in that 140 HR neighborhood on your easy running - is that too hot? I don't know, maybe. But not something worth working on until after this cycle is over. Regardless, I've noticed you've done a good job of staying around there, but in the runs leading into Sunday's long that HR creep was loud and clear. Compare what you did in the lead-up to this long run to the prior two:
7/3 HR by mile: 140-147-149-153-153-154.
7/2: 135-142-147-152-152-157.
7/1: 138-143-148-149.
6/20: 133-136-141-142.
6/19: 133-138-132-123-137-146-153
6/18: 140-141-141-142-143
6/13: off
6/12: 137-143-141
6/11: 138-145-142-146
You did one mile total > 150 in the three days heading into the weekend long the last two times. But this week you did 6. And a few more in the high 140's. So while yesterday's long run conditions were quite miserable and played a big role in the demands it put on your body I think that cumulative effect throughout the week also played a role on that particular run. Mother nature isn't something you have control over, but effort on easy runs? You do.