I'll answer / respond to a few items...
*my husband is now working in a company with payslips since april 2011
The embassy really requires 6mnths' worth of payslips, to show that he's in regular, continuous employment.
Obviously you haven't got this..... so the choices are to wait for at least a few more months (best), or to provide a covering letter of his "history" of employment, perhaps over the last 5yrs, and show how the situation has only changed (ie employment) because of his commitment/visits to you.
*my does not have much savings in the bank
It's not just in the bank.... does he have shares, ISA, a pension plan (that kicks in at a later date) ?
It's all about convincing the Embassy that he can support you now & in the future.
*my husband is living with my parents-in-law
(I assume you mean with HIS parents ?)
If so, to be honest, their health is of no concern to the Embassy (sad as it may be).
What you do need however, is a letter from them stating that you & your husband & son can live there. (If they are renting, then the landlord also has to state that he's OK with this arrangement)
Additionally, you need to prove that the accomodation is sufficient for all these persons ie at least 3 bedrooms. U need photos, council tax bill, etc
That's my two-pence worth.
