When I purchased my 0805 from GB, I already had focus issue and already had same "unremovable" glue. I know you're already opened it up (I did, too), but for others who has same issue:
1.)- If you has any serios issue with your dashcam bought at Gearbest, you should contact Gearbest BEFORE you open it up. Why? Beacause they'll offer 3 ways to handle your complaint. You can chose partial refund meanwhile you keep the item. (but they'll need pictures and videos about the faulty, unopened product).
2.) AFTER that you can open it up. I had same ****ty glue on mine, and tried to remove it with a scalpel for an hour... Followed the screw thread and tried to remove as many glue as possible.
3.) For me i had big luck this part, but probably you can broke your lens. When I tried every solutions I could try (scrape, heat, solvent) and noone worked, I was very angry, took pliers, and tried to screw off with force (as I remember well CCW). Big *click* sound.... I think I just broke my lens.... No, I was lucky and the lens released!