Have you considered how many minutes total in a month the faster download will save you compared to all the time you spent trying to "fix" it. Things like steam are really stupid too. I have full gigabit and steam many times downloads at a much lower rate, it varies a lot between games. The even more intesting thing is it will download files stop downloading and update disk then download some more rather than do both at once. It tends to take more time installing and doing other things local that it takes to download the game.
You largest issue is you have been mislead into thinking that wifi number you see is the actual speed you can get. The router manufactures for a while have been playing the game who can tell the bigger lie to get a bigger number.
The wifi guys would call 1gbit ethernet 2gbit because they like to add transmit and receive speeds together. Unlike ethernet which can actually send and receive 1gbit at the same time wifi is half duplex and only 1 device can transmit.
So this cuts the actual wifi speed a lot and the more device active the more inefficent it becomes. In addition this all assume you are in some room with no interfernce with very strong signals. Any interference or lower signal levels will reduce the number even more.
In most cases you should never expect more than about 300mbps on even the very fanciest 802.11ac stuff using things like 4x4 mimo that few device support.
The 250 is not out of line with what most device get. Why your PC runs slower you are going to have to try to see what is different about the connection rate. The actual connect number you can look up in a table called MCS. Maybe it will give you a clue but other than maybe your pc is connecting using
some older data format most this stuff is negotiated between the router and the PC to get the best option.
In most cases there is very little you can do. You can do very little to solve interference from outside your house and the signal levels are mostly related to where the device is located and what is in the path.