From what I am told, it was a way to educate the youth. It wasn't meant to educate them on religious matters, but rather to educate them on arithmetic, reading and such. In an agricultural society in the 1700 and 1800's they had little time to learn math and reading. The Pastor probably was schooled in both. It wasn't a religious thing, just a way to educate the youth in the absence of a public school system.
Don't know... But there is nothing that says its wrong.
As for tents, evangelicals wanted to preach in the 1940's and up... It was a matter of renting a building or having a tent to preach in. Its costly to buy a tent and chairs, but if you are travelling, eventually its cheaper than renting a venue.
As for camp meetings, I see nothing wrong with folks doing that via scripture.
Nothing wrong with that. There isn't scripture that says you can't pray on Wednesday. Is there scripture that says you can play bingo on Wednesday? Yet I see Catholic institutions that do so... I don't bother them about it because I don't have a scripture against it.
I am unfamiliar with that. Yes, I commune with the Lord when I go to Church and hear his Word. That is in the Bible.