You can get JSA as long as you are not in what is called remunerative employment which means employment of sixteen hours or more each week. As you are working eleven hours, you can claim it. The allowance for a single person aged twenty-five or over is currently �60.50 per week.
The same sixteen hour limit applies to income based JSA and with that you can claim for a dependent and receive �94.95 per week. There are additions called premiums for those wi a disability or family for example which increases the basic amount. For these cases a claimant can keep the first �10 or �20 of earnings dependent on their circumstances and the benefit is reduced by the amount above that particular amount
You are correct in what you say about the National Minimum Wage and just under the sixteen hours would be �91 odd but only �86.odd would be taken as income. That exceeds the amount you will get but for those getting Income Based JSA (which you may qualify for in six months� time) it may be less than their JSA entitlement.