A neighbor of ours used that to fix a hole in a plastic sink drain line in sticks and bricks house after they drilled into it. Held for a while (or they knew not to use upstairs BR sink). Unfortunately the new owners had a major problem and had to tear out a wall.
Sooo. I would put in new tank. A 'weld' may work, but do you want to risk it failing while on a trip? I dunno what should be used to glue sewer line to tank. If its all abs tho I've used a glue made just for that from Home Depot. Its very fast acting so gotta connect right first time.