@-moz-document domain(mail.google.com) {
	.nH.OH0apf { display:none !important; }
	.Bs.nH.iY tr td:nth-of-type(3) { display:none !important; }
	.nH.oy8Mbf.VKRe2c { width:174px !important; }
 }

Do you see more?

Edit your Firefox’s userContent.css (ChromeEdit makes this very easy)

@-moz-document domain(mail.google.com) {
    .pp {
        margin:0px !important;
    }
    .q0CeU {
        margin-right:0px !important;
    }
    .nM .n3 {
        margin-left:0px !important;
    }
    .Bs.nH tr td:nth-of-type(1) .nH.oy8Mbf {
        width:160px !important;
    }
    .Bs.nH.iY tr td:nth-of-type(1) .nH.oy8Mbf {
        width:100% !important;
    }
    .Bs.nH tr td:nth-of-type(4) .nH.oy8Mbf {
        width:192px !important;
    }
    .Bs.nH.iY tr td:nth-of-type(3) .nH {
        display:none !important;
    }
    .T0 {
        border-top:none !important;
    }
    .GcwpPb-Z8OBDd {
        margin-bottom:0px !important;
    }
    .qRauBc {
        margin-top:5px !important;
    }
 }