for getting the 510 pin loose use a good not cheat screwdriver the full size of the slot in the screw or as close as possible now stick an allen wrench into the air vent hole in the base this will give you something to grip against and lever with. If it still wont budge you can shock it out, you will need to mount the base in a soft jaw vice or a hard jaw with a rag to prevent buggering it up. I suggest still using the allen in the vent hole against the vice jaw to prevent spinning, now put the screwdriver in the screw slot turn it with pressure trying to remove it and hit the top of the screwdriver handle with a hammer this should send a shockwave
through the screwdriver into the screw and cause it to jar loose, may have to hit it a couple times. for the bottom
tank ring stick allen wrench in the vent hole wrap the ring in a cloth and grip with channel locks should unscrew easily then.