Sediment broken free in pipes has likely caused lower water pressure

Back flush it to where? Unless you have a way to purge it outside, it will just come back and clog it again.

There is a whole janky looking spigot and sprinkler system out back where the water comes into the house. I'll just remove a couple of spigots and purge it out back.

I found the shut off by the water meter so I was able to change the water main coming up into the house. The line that goes into the ground is basically about 40% clogged with rust. That's not the source of my problem since my water pressure was decent enough just a week ago with the pipe like that but it's still concerning.