Lord Ebola

When you say that your internet is faster, how do you measure that? Does if feel faster or you did a speedtest? What was the difference? And we're speaking about wired speed right? When you're not using the switch, is the PC connected in one of the LAN port on the Airport (There's a small <...> symbol above them I think)? And as Lurick said you definitely need a router instead of a switch, I would return it If I were you. Why can't you use the airport though? It IS a router.

It depends on your budget really. I love my Asus ac66u and always had good experience with Asus routers in general. Not very expensive and does the job pretty well. You got 802.11ac for bandwith heavy apps, dual band antennas to play around interference or range/penetration issues and Asus firmware is very good out of the box. Also all the Ethernet ports are gigabit and it handles high speed transfers pretty well in my experience. Keep in mind that it might not be the best suited if you have many clients requiring lots of bandwith (Say 4-6 people streaming video and gaming over Wifi at the same time), in that case you should look at more expensive routers that supports MU-MIMO, they usually have many antennas and look a bit peculiar like the asus rt-AC5300 or Netgear Nighthawk series. That being said, if the majority of large data transfer and routing intensive traffic is on the wired LAN, don't bother too much with very expensive routers(250$+), just make sure the ethernet ports are all 1gpbs (on the switch too!) and that you have 802.11ac dual band antennas and you will probably be fine.

If you are sure that the problem is not present with another router, try hard resetting your TP-Link router.

Depends on your budget really. I personnally opted for an Ikea Counter top and bought height adjustable legs that I bolted under. Unexpensive and very sturdy.

Speeds over wifi are greatly dependent on the access point you are using and the level of electromagnetic noise that is present in your environment. If your access point supports it, make sure to use the 5ghz band as it is way less impacted by interferences. Then do not be surprised if your speeds/stability are not consistent. It is the nature of this technology and if you cannot tolerate it's quirks you might be better served by a good old cable. Did you know about power-line Ethernet adapters? They are a great and cheap alternative to Wifi. https://www.cnet.com/topics/networking/best-networking-devices/power-line-adapters/

Try putting the IP of the server as the default gateway on the client and the other way around(Client as Server's gateway). Also tryout with a crossover cable to be sure that the NICs detection is not being problematic like Endeavor01 said.

On recent routers there is a function that is called Band Steering that will automatically switch between 2.4ghz and 5ghz frequencies depending on your local environment. I suggest that you deactivate that in the firmware and only connect on your 5ghz network.

I don't understand. What couldn't you get from the drive without booting on it? Files are not magically created when you log on a windows account. If you can mount the drive on another computer and see the files, you see everything that is on there.

What's the make and model of the switch? You say that it doesn't work with the switch, could you explain what isn't working and in which config(What is plugged where and with what)?

Like others said, I cannot recommend a free VPN. I HIGHLY recommend you find one that is not too expensive while being trustworthy. If you are interested in unadulterated facts on almost all VPNs, look at https://thatoneprivacysite.net/ That is, hands down, the best independant ressource to make a choice of VPN in a market that encourages shady and greedy businesses.