The antivirus you use (avira) is pretty strong.So no comment on that.But you just said you use windows defender/MSE for on demand scanning.If you use windows 7,then you must uninstall MSE if you want to use avira free.If you use windows 8 you must disable windows defender while using avira.Because they are stand alone antivirus programs and may cause severe conflict.If it is windows 7 and you scan with windows defender on windows 7 then no problem because defender on windows 7 is antispyware only. As you don't know about which setting is applied to UAC on your machine,it is likely to be set on default.As for on deman scanner you can use MBAM and hitman pro.you can use a backup software like macrium reflect.As you have stated that you will start VM malware testing so I am not suggesting you sandboxie.everything else looks good.