Board Thread:Writer's Workshop/@comment-10502460-20181206012011/@comment-10502460-20181206055709

"Some of them were very active in the church, and a few of them were volunteering for the Advent season to help with the food drive and fundraising for orphans."

I would write this as

"Some of them were very active in the church. A few were volunteering for the Advent season to help with the food drive and fundraising for orphans."

Personally, I think it cold go either way. You seem to have something of an aversion to sentences containing more than one or two clauses.

"David's grades were not good enough to get into college, and recruiters from all four branches of the United States military had told him he was just not a good fit for their service."

I would change this to

"David's grades were not good enough to get into college. Recruiters from all four branches of the United States military had told him he was just not a good fit for their service."

I might even change it to

"David's grades were not good enough to get into college. Military recruiters had told him he was just not a good fit for the service."

Although I don't consider that a run-on sentence, I do think your second suggestion is the best version.

The next one follows right after.

"David became bitter that he had just missed Vietnam by a few years, knowing the military would have taken him then because they needed as many volunteers as they could get after the draft was abolished."

I would rewrite this as

"He became bitter that he had just missed Vietnam by a few years. The military would have taken him then because they needed as many volunteers as they could get after the draft was abolished."

I changed the David into He to improve variety.

I agree with that suggestion.

Here is an extreme one, IMHO.

"Well," Uncle Thomas tugged at his beard in reflection, "if you wanted to play devil's advocate you could say maybe they just wanted to send a message by destroying the building itself, and intended to minimize collateral damage by setting off the bomb at a time when there weren't many people.

Well, that one is dialogue, and to me the more sprawling sentence structure more accurately reflects a conversational flow. Though I suppose it could be changed to Uncle Thomas tugged at his beard in reflection. "Well, if you wanted to play devil's advocate you could say maybe they just wanted to send a message by destroying the building itself, and set the bomb off when there weren't many people to minimize collateral damage."