I need a drum roll
because I am about to do you the biggest favour ever. I don't need to address any of your questions or individual requirements because there is one solution which is going to fix everything for you.
Shub1 is cack and the wifi is beyond cack. I think shub1 came out in 2008 so everything else aside, the wifi technology is ancient and was horrendous even when the shub was new. Shub1 is famous for its appalling wifi and it is well documented.
I am glad to see you are looking to invest some £££ because the absolute best thing you can do to help yourself is put the shub in modem mode and buy yourself a proper router just like
this. If you get yourself a proper router the wifi will be far superior to what you have got now and there are many other features you can play with which will enhance your internet experience. I can recommend cheaper routers but you defo need to be looking at an AC router so you know it is going to last you for a while.