What all I should do or need to change my status from H1B to H4? When should I start doing the process? Is there something I need from my employer or my husband’s employer who would be holding my H4. My current employer is not wiling to do COS for me
H4 is owned by you, not by any employer. All you need to do is to file for a H4 Petition using your spouse’s approved H1B(I-797 notice of approval). This can be done by yourself, you dont need it to be done by either your H1 employer OR your husband’s H1 employer. Generally, for most of the cases, Your spouse’s H1 employer does this as a courtesy. Please contact your spouse’s H1 employer to get your H4 filed. (Again, your husband’s employer or any other doesnt hold your H4, its all yours. Only H1s are being owned by the corrosponding employers).
Adding to this, If I am searching for another job but no longer work with any employer who holds my H1B, how long can I be on H1B status; before I actually change the status to H4 (if I dont get anything suitable)
There is no statute depecting the length of legal stay once your H1B visa(as a matter of fact, for any such visa) is not valid any more. But logically, government allows(not guaranteed all the time) 10 days(again, its an assumption, no real law allows any single day). So, try to find another employer to file your H1 transfer by finding another job in 10 days, if not, you better initiate your COS to H4. But lets say that your H4 COS filed, not yet approved but you found another H1 employer a job and a transfer initiated, you can always cancel your Original H4-H1 COS filed by you(before this COS is approved).
Also, if I want to change the status from H4 back to H1B, will I again come in the H1B cap or I can used my unused petition from previous H1B
You are not going to come under H1 annual cap if you still have any time on your current H1(less than 6 years of its H1 status use).
Summary: If you can properly plan, you can easily mitigate your situation. You have plenty of time (3 more weeks of your PTO). Market is real good. Try to get a job ASAP, that resolves all your issues. Good luck.