Prior to the PIRATE act of 2020, running a pirate FM station was effectively legal until the second time you were busted. Prior to 2020, if you shut the station down after getting your NOUO, there wasn't any real penalty. Teenage me loved this, and my buddies and I had a little irregularly-broadcasting pirate radio station, using a cheap CZH-7C transmitter purchased on eBay. One time we went on air from our high school's cafeteria during a study hall, and surprisingly, nobody questioned anything! We did have Microsoft Sam narrate our broadcast so that we weren't making a ton of noise.

We never did get our NOUO; instead, we ran into the much bigger reality, which was that none of us had anything of interest to say. After the novelty of hearing our voices on the radio wore off, the transmitter ended up in a closet, where it probably still sits today. Good times!

If this is completely non-commercial and you have an amateur license you could probably use AREDN as a backhaul instead of HaLow. We've gotten wifi going from a panel in Elysian up to Wilson on AREDN.

100w from the Verdugos should be pretty substantial. I regularly make 70cm FM contacts on 446.500 from Elysian Park down to San Diego at 5w.

The technical side, while interesting, is relatively clear to me. The legal side, including cost, is something I have no idea about.