Ultimately it depends on your goals and that’s for you to decide. From a physiological standpoint, there’s no on-going processes that get disrupted. You’re just not fasting on those days.
My personal approach is to not worry about my schedule so much on the weekends - I’ll stick to it if I can, but still try to eat roughly the same. I’m mostly focused on weight loss, so this allows me to keep it rolling without worry so much about the exact schedule lining up with life.
Have you considered shifting your window on those days earlier? Maybe having a big breakfast and lunch and skipping dinner? If this won’t work for you you will still benefit from fasting the other 5 days.
Sure. Just think about is it tough because you’re tired or does your body really need the food? If you’ve been snowboarding all day, you may be genuinely hungry. It’s really hard to skip meals in social situations where other people are eating but you get used to it. I try to decide ahead of time and not in the moment. It’s okay to decide to not do IF some days. I’m at maintenance and it doesn’t seem to affect my weight at least to have a longer window once a week or so.