I assume you're combining the ascorbate with a phospholipid when you make your liposomal? otherwise it's not liposomal.
No idea about shelf life. At a certain point when things get too complicated you're probably going down the wrong road.
I do post a lot about pills but in reality I am not a fan of pills. Always try to source nutrients from foods first and turn to pills later if that doesn't work.
During my pineapple days I realized that a lot of the number madness with enzymes (read claimed dosages) are just bullshit as pineapple juice was better than any enzyme pill I took - even high doses.
Whole food sources of c contain flavanoids as well to make the c actually work. Another trick to try with ascorbate is to take tiny doses many times a day, something like a pinch every 1/2 hour or so or even more frequently.
Broccoli and cabbage also contain a lot of vit. c, but you probably want to stay away from those while your thyroid is wack.
I still think you should re-read my original response when I mentioned gallstones. When I hear stuck throat that is my first guess.