Why can’t I get a torsion spring tension level that works for having the garage door both open and closed

Check your sensors. The sensors could also be very dirty or blocked by something.

Openers also often have cutout sensors that will stop the drive when the load gets too high on the motor. It may be that the load in your case may be too high due to wear, dragging rollers, bent track, lack of lubrication, or rusty chain/screw. Look for these things and correct if possible.

The overload cutout sensors are often adjustable and may be set to low and thus need re-adjustment.

Probably by unhooking the opener, operating the door manually, noting were the problems are, and adjusting or lubricating or replacing bad rollers to restore smooth operation by hand, leading to smooth operation by opener.

If there are no problems, sticky spots, difficult areas of movement when operating by hand, the opener itself becomes suspect. Aside from checking it for needs in the lubrication and adjustment realm, that quickly bifurcates into

1. "replace the whole opener" (advantage - guaranteed item)

   or

2. "start replacing parts" advantage - CAN be cheaper if the parts fix the problem. Disadvantage - parts are often not returnable and may not fix the problem, depending what the problem is, so there's a potential for it to cost more if you end up needing to replace the whole thing anyway.