As long as you aren't married to an NBA player, I think you'll be totally fine. I wouldn't even blink at an inch short of 7'. :-D

Personally, anything over 6'-5". Generally, a lot depends upon the space it is going in.

That 6’ 11” is only if you mount that 25”H fixture right at the ceiling level. Presumably you are not talking about a ceiling mount light, because that 25”H would be massive for a ceiling mount.

A pendant needs hanging space above it, just as it needs traffic space below it. It should be self evident that you have to also factor in the distance of the chain to the 25”H fixture, and that 12” isn’t going to do it, as it wouldn’t be proportionate. Your 25“ fixture cannot be over a walking space. It must be over an island or table. Some place that people do not walk. Because by the time you account for the drop needed, it will be much less than 84”.

Depending on which area of the house it is, it can be okay as long as you don't have anyone too tall in the family. But if it's a living room or dining room where you will have guests over a lot, I would be worried that someone on the taller side may accidentally hit it with their hands.

I would be more concerned with light near eye level.

This totally depends on the design of the fixture, the space, even the type of bulbs being considered. Post photos of light with sizes, space if you want a correct answer.

We don't know anything about your actual light, but if we were only considering the clearance under a light, I think you can impinge on 7' a little without much issue. I would not go below 80" especially at your front entrance. A lot of things, including new furniture, maintenance supplies, etc come through front doors, and the lower the fixture the more likely it is to get in the way or get damaged in the process.

The finial at the bottom of our foyer light hangs at about 79-80". No one we know is tall enough to hit their head on it, And it does occasionally get in our way.