If you don't have a propencity to MPB , and if running high dosages of testosterone never effected your hairline then you 'should' be fine running Masteron . I've ran over a gram of test a week , and run high dosage of masteron quite often and don't notice a difference in hairline.
no you cannot use a DHT based steroid in place of test. it will not have any effect on your sex hormones , only test (and ment) can keep that functioning . if you ran masteron with no test , then your natty test will be suppressed and you'll suffer from symptoms of low T , like brain fog, low sex drive, erectile disfunction.
If your run a low enough dose of Test as your base, like 150mg a week , then you won't nee an AI more then likely . just run that with your Masteron and Var and estrogen shouldn't be an issue