TOILET TANK LEAKING INTO BOWL - HELP

I can hear the toilet running at night (second floor) so after investigating it appears that with the water turned off and the toilet is flushed until all the water is out, and then the flap is removed, when I look down into the opening the flap covered, water is dripping down from the end of thhe plastic molded pipe into the well below. It doesn't stop dripping until the tank is nearly bone dry, but it does drip much more slowly as the water level approaches zero. There is no water on the floor. I figured there was a leak either at the seal between the pipe and the tank or a leak very low down on the pipe, near the bottom of the tank. SO (I've probably made a mess of things now): I took an epoxy that works underwater made for repairing boats and tried very hard to place it all around the pipe from the bottom of the tank up to but not including the lip where the flap sits. Still drips and I can still hear it and the water level in the tank visibly falls as you watch it. I tightened the bolts that hold the tank to the bowl as much as I'm able - it still leaks.
When I wobble the overflow tube the whole lower portion where the flap covers rocks. It doesn't rock differently now that this epoxy (it's flexible) is in place. I got this epoxy 5 years ago after a batch of it I'd bought for the boat was absolutely astonishingly successful in patching a spurting water main that had broken IN the wall and I'd just bought the house and couldn't find the water meter to turn the water to the house off (turns out the meter was in the woods at my proberty line about 400 feet away). I was able to stop the water from running inside the house, at least, using this stuff. I wonder if it is too old after 5 years....
Should I get more of this epoxy and put it absolutely everywhere in the area or should I take the tank off? Once I take the tank off, what do I do?
I've checked all the posts on this group about leaking toilets and one fellow commented that too high water pressure can be the cause of this...and I know my pressure regulator valve is not working (pressure is 90, should be 80 or so I think..). Could this be a factor?
I'm really trying here. I'm not incompetent - replaced the first floor toilet a few years ago mostly uneventfully - but I don't know now. Don't want to take the tank off (messy, complicated, tanks are hearvy and I'm a girl) but if I do is there a seal or something I should buy first and what am I going to find once I get it off.
If any of you fellows could guide me here, I'd appreciate it.
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get rid of allt he epoxy, make sure the tank isn't cracked. replace the fill valve, the flush valve and the tank to bowl kit. this is doable...even for a girl. all ya need are the right tools, and a bit of luck on the part of the old tank to bowl bolts coming off nicely
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