How to deal with water damage from backed up AC drain
The drain pan should have a limit switch/sensor which prevents operation of the unit if the sensor detects the pan is full. Either this switch/sensor has gone bad or was never installed to begin with. I've never installed/replaced such a sensor so I cannot state how hard it would be to do so, but my guess is it should be fairly simple.

The condensate is not pure water. Sometimes it can seem more like syrup--at least that is what I have observed. There are various options. Periodically adding vinegar is one option. Bleach is not recommended. Note, you can also have this issue in winter if you have a high-efficiency condensing furnace. You definitely should clean the drain out bi-annually. Quarterly would be better....

If it were mine, I would probably rip out the flooring and replace with tile or vinyl depending on how visible the area is and how often it is accessed. This flooring appears to be some type of cheap laminate (read that: not worth trying to fix) in my humble opinion.

Read more here: https://www.artplumbingandac.com/air-conditioning/how-to-unclog-an-ac-drain-pipe/