Need help with Win10 on Inspiron Mini

I own a Dell Inspiron Mini {serial number D3JVZL1}.
I am experiencing three problems after upgrading Win7 Professional
to WIN 10, namely,

    1. I cannot install any applications from the Win 10 Store. When I try
        and download any app, I do not get an "install" button but the
        "free" button remains showing, so that installation is impossible.
    2. All windows are shown at a resolion of 1024 x 600; control buttons
        get hidden behind the bottom of the Win10 window. Control is not
        therefore possible and the corresponding app is unusable.
    3. Windows Defender tells me it is trurned off; I cannot find a way to turn it on.

I cannot find a display driver to give me a resolution of 1024 x 1600 or vertically higher.
        
Do I go back to Win 7 pro (I have a disk) then upgrade to Win 10?

Nicholas Solntseff
n.solntseff@rogers.com