u/BenDisconnected

I wanted to add some wiring between the joists for a ceiling fan downstairs. But I found this board next to the joist in red after i started cutting the subfloor open. Is it safe to cut out a 5” hole here to do the wiring underneath?? This is a second floor on a townhouse where floor joists are ~20in apart. This is roughly the center of the house from left to right and the center of the living room

Im getting a drop/min in this new water heater DIY connection. It was installed with tape, pipe dope, 2 10in wrench, and average human strength. I replaced it with a new sharkbite and a new nipple already. What should I do?