Your experiences are noteworthy and further confirm my concern.
I clip on to the lifelines for a day sail, but for long distance cruising, always have bow to end-of-cockpit jacklines. Those are good and mandatory. But the problem remains about how to avoid getting towed forever.
When cruising, I trail a dinghy, and consider that my ultimate last resource to get up - but as you point out, I need to disconnect the tether to get to it, and that involves significant risk. Maybe I should carry a 3/16" line long enough to go from the tether end to the dinghy, so that I can be always attached as I go backward towards the dinghy. Interesting idea. When considering the dinghy, I wasn't certain if the idea was realistic, but your encouragement makes me think it is and should be taken more seriously.
I carry, connected to my lifelines about midship, a bag which contains a ladder. Extending down from the bag, is a pull line. Right now this is only on the starboard side. Perhaps I should get one for the port side as well. If anyone is interested, this ladder is available commercially (but not from the major supply stores like West and Boat)
I have also removed the water activated autoinflate from my pfd, figuring that if I am dragged, the additional drag from the inflated pfd may preclude me from manoevering in the water or working my way up the ladder. I can still pull the pin for the manual autoinflate and it will inflate.
Lastly, this year, when cruising, I have connected my portable VHF to my pfd so I can radio a mayday. However, the pfd's don't have a way to have them connected to the pfd. The pfd belt is too big for the VHF bracket and it keeps falling off. I will need to get an additional strap sewn on to my West pfd this winter.
But if the boat continues at 5-7 mph, and perhaps the motor is still going, and the autohelm keeps it right on course across the ocean, perhaps there is no way I could get up or even move around in the water. But there must be.