1995 Chevy Cavalier Recovery tank overflowed after opening

I've had a coolant leak for a few weeks, and it's gotten bad in the last week. I did not see any coolant around the top of the overflow tank, like I did two years ago when there was a compression leak, so I wasn't too worried about that. I did, on the other hand, feel coolant around the bottom of the water pump, which is on the other side of the engine, and near where the coolant ends up on the ground, so I assumed it was just a common leak at the water pump gasket and I could drive it for another week before getting it fixed.

I've been checking the coolant level before and after each drive, and it drains quite a bit, but I fill it back up again. Maybe 1 gallon for every 2 hours of driving.

Yesterday I put Stop-Leak in it to try to slow it down until the weekend when I get it fixed. After I drove to work this morning, I shut off the engine and opened the recovery tank, and it was at a pretty normal level. I was pleasantly surprised, since it would be almost empty the last few days when I did this, so I assumed the Stop-Leak had helped.

I went to get the coolant jug to top it off, and when I got back to the front of the car the tank was overflowing.

Would this happen simply because I had opened the recovery tank cap while hot, releasing the pressure and allowing it to boil and push the coolant out? Or is it a compression leak again? Overflowing the tank like this is exactly what it would do when there was a compression leak.

Can I safely drive it home?