Ariric,
Unfortunately I am no longer with QP (I left in 1997) but there are threads on this site that will give you an indication of salaries/conditions being offered within QP and the country in general.
If you are uncertain about anything, contact QP, I am sure they will respond.
Allowance for electricity, I believe that QP still allow a "useage" beyond which level will be for your own account, similarly with water.
Telephone provision I understand that at SS level, the installation and rental is paid for by QP. Local calls are free in Qatar but international calls will again be for your own account.
The above should be checked with QP to ensure that my comments are valid.
Forget re-negotiating the salary when you arrive. There is little mechanism for making adjustments.