Bars stop leak or other will not hurt anything, IMO, but certainly won't cure a leaky water pump. Water pump has a dynamic rotating shaft seal that is leaking in your case. Stop leak works by plugging a static hole, and a loose rotating seal will not seal w/ this type of product.
A small amount of weepage from the water pump drain is OK, but a steady drip and puddle after stopping is not.
One good thing about a leaking water pump is they will run for some time, and will get progressively noiser (bearing lube being washed away) before failure. You don't have to immediately repair, but don't put off for too long, perhaps 1-2 months. If the water pump freezes, the timing belt could break and timing between crankshaft and valves would be lost, w/ damage to valves and potentially pistons which will hit the valves.
See you down the ROW!
1999 Subaru Forester