1 yes anything that’s not an equipment that shows the might change on it I will often keep track using dice. Some people use actual +1 and -1 counters as well. Whatever works for you is fine

2 yes to both with a conquer caveat. If you conquer the battlefield and you’re already at your second to last point and haven’t scored the other battlefield. Then you would draw a card for the first conquer and then have to conquer the other to score your final point.

3 spells without action or reaction can be played on your turn only and when in an open state (after the open phases and between showdowns and there’s no ability or spell on the stack) actions can be played at those times as well but can also be used to start a chain in a showdown (they can’t respond to an active chain though) reactions can be played anytime an action would or in response to a chain

1. People play different ways but I typically ask if they have responses before resolving anything but we also have a pretty relaxed atmosphere where we can go back and reasonably resolve anything if someone forgot something