If i travel to another city (from Toledo Ohio to Detroit Michigan) to teach at sunday school and I want to do my wajib fast. Can I fast and then travel to Detroit and come back to Toledo before maghrib. Will my fast be valid?

2) If one is a type 1 diabetic with an insulin pump and needs to make sure blood sugar is not too high in the morning otherwise they get very thirsty and it is difficult to fast. Can they wait until morning (2-4 hours after Fajr) and see if their blood sugar is normal to decide if they can fast that day? Its for wajib qadha fasts.

3) On same instance if they decide not to fast that day in the morning around 3-4 hours after Fajr is it haraam because before going to bed at night they hoped to fast the following day?

1) If you travel after Zuhr then you can fast as normal. If you travel before Zuhr then you cannot fast.
2) You can make the niyyah for a wajib fast any time before Zuhr as long as you have not done anything which will break the fast
3) No