Is the tense used in the sentences correct?

Jennifer had been stopped to help Jack. Alex hadn’t wanted her to help Jack.
Jennifer stopped to help Jack. Alex didn’t want her to help Jack. (Past Tense)

Note:

Jennifer had been stopped. = Somebody else stopped Jennifer (whether she wanted to stop or not).
Jennifer had stopped. = Jennifer had stopped because she wanted to stop.

CJ

CalifJimJennifer had been stopped. = Somebody else stopped Jennifer (whether she wanted to stop or not).

Interesting that my experience has been that there is a usage that goes, "to be stopped' is to be in a stationary mode on the highway. On some highways, it is not legal to be stopped (of one's own accord). Thus, the perfect tense would still be "Jennifer

wilpeterthere is a usage that goes, "to be stopped' is to be in a stationary mode on the highway

Yes. I was stopped (adjective) at a traffic light. But following a stative with an infinitive of purpose is an absurdity.

I know how to read (in order) to help Jack.
Laura understands Arabic (in order) to help Jack.

I'm not arguing, but am intrigued.
The TV was turned off when I entered the room.
Can this not mean both: Someone turned it off when… and It was already off when… ?.
The 'mode' becomes an adjective?

wilpeterThe TV was turned off when I entered the room.Can this not mean both: Someone turned it off when… and It was already off when… ?.

Yes. It can mean either one. Under your first interpretation "turned off" is a verb; under the second, it's a linking verb (was) and an adjective (turned off). (My instinct would be to use the second interpr