Seeing as your situation somewhat requires stealth and precision as far as adjustments go. Here's what I would try.
You can google how port forwarding is done on your router. Make an hour of it, read all the results with a title that seems comparable. Watch several of the YouTube videos it suggests. After awhile the rubbish info will fade, and the relevant info will begin to become more clear. Google what all ports need forwarded for the PS5.
After you've done that go have another look at your routers settings. Little things like making sure you disabled Upnp prior to forwarding ports will make you give up technology altogether. Make sure you've got all the right port numbers in the right boxes. Make sure the correct static IP address is set to your PS5.
Looking back through your comments, there's definitely some additional things that you might not have considered. Am I correct in believing the 3 following things?
1. You have $5-10.
2. Your connection enters your house with an ethernet cable that comes up through the floor?
3. Your PS5 is wired directly into your router?
If those 3 things are true, there's an incredibly simple path to bypassing your router, and thus giving you a far better indication of if your problem is with your router or your ISP.
Go to Best Buy. If that's not doable, go on Amazon, if that's a no go, go to Home Depot. If none of these are an option, go find the nearest isp company, tech whatever. Pay the $5 bucks for a double female ethernet connector. Tell your parents that some there's some lost looking dude from the Publisher's Clearing House out by the mailbox holding a ridiculously oversized check. Once they clear the porch in a full sprint, take your newly acquired ethernet connector, unplug both the wire going into your router from the PS5 as well as the one coming up from the floor. Connect them together with the connector, and go see what the results are on the PS5. Don't worry, you've got plenty of time. Your parents will still be desperately searching for the Clearing House fella. Even if they've figured out your distraction, they'll be so out of breath that time is still on your side.
If it works, it's the router, if it still doesn't work, it's your ISP.
i know I've set up static ip and port forwarding correctly.
But your other suggestion, I'm definitely going to try that. never even occurred to me to try finding a way to bridge the cables. thanks, still might not be able to try it for a couple weeks but that will be what i try next. Thanks!!!!!