You need to ask QP that question. Allowances have nothing to do with Qatar Immigration or Labour.

If you sign a contract, you sign a contract. If it doesn't say "if your spouse gets allowances from another employer we will stop paying your allowances" then I don't see how they could retract.

Assuming you are coming on 'family' status allowances, if your husband gets a job with QP as well, then you would obviously both be sharing ONE "family" allowance package, not two. Fair is fair.