From the sounds of your post, you are fighting environmental issues. FCC RF signal strengths have not changed over the last decade. So, upgrading your access point to newer equipment is not going to fix your problem. You need to move your access point.
Your options are to try and use some of your existing coaxial cable already in your house, use your electric wiring in your house or fish some new cable through a fresh air return of your central air ducts to a new location.
You can pm me if you want more details.
If you are still looking at a new access point then look at something with a firewall and Antivirus built in to secure various IOT whole house devices.