Yes,of cause we can do the Forex trading as full time job,this is more better.Full time in Forex trading can giving you more time to get analysis and care about the marketing mover,using the time enough can get know more about every currency or commodities.Most the pro trader was working trading in full time,even now many person was retired also having trading with the time.
and it varies form person to person . those who have much free time they can take forex as their full time job n those who do not have spare time we take it as parttime job. as far as earning is concerned, it also depends upon the ability of the person if he has good knowledge and experience about forex then he can earn enough money that there is no need of other job