I’ve been there. I ended up buying an ASUS-RTAX53U, flashed it with OpenWRT, since it supports VLANs. You have full control over your device. For switches I’m using zyxel 8 port managed ones. Having 4 ssids, Im satisfied, and can be done pretty cheap. If you want to get started check OneMarcFifty’s tutorials.

Can be a lot of things. For my parents problem was the old lan card in pc, which was 10/100. Can be router port, switch port, cable. How do you measure it? Can you plug ur pc directly to the modem or router?

Mesh or wireless bridge?

Even if your port is forearded, make sure 8096 is allowed through the firewall of your computer. Also make sure you are not behind a cgnat if you want to access it externally.