Trust me, there is no such thing that over qualify to the job. Only how much of salary that you feel reasonable to be accept.

If you insist to support your family. You have 2 option now,
1) Study PHD in part time while working in full-time.
(This is what i currently do )
2) Focus in working.

Nowadays in this market, certification is just the ticket to entry job, it does not mean a higher qualification equal to higher salary & chance. Working experience is the key to further your career.

If you spend your 4 year full time in PHD, i rather you to get 4 years working experience while you are young. You might become a manager if you working tough enough.

Frankly, what do you expect your job designation that the company offer to a PHD student with no working experience ?

Quick and simple.