For the housing allowance, this is the correct range with no kids I would say.
Careful, to be honest, this is the worst situation to be unmarried and a woman... You can come on your own, but cannot sponsor your partner this means he cannot live here as a resident... This also means he cannot work since he would stay only on tourist visas.
And even if you are married you have to think it twice. A woman cannot sponsor her husband (the opposite is possible). Means he cannot work under your sponsorship and has to find a job that wants to sponsor him, can be easy, sometimes it is not.
Bottom line, get married, and find a job for you husband BEFORE coming to Qatar. Finding a job really depends on your field.
Concerning exit visas, this is true, but some companies give permanent exit permits. For the home leave allowance it also depends of the company, some give an average amount, some pay the tickets.