I assume that the LC you received is for your spouse not for you, right? If the LC is based on your current position, you cannot quit. You need to wait for at 6 months after your 140 and 485 filing to switch the job. Hopefully, your attoney can submit them before 9-30 to beat the Oct. 1's dead line.
You only can apply EAD card after your 485 submission. Once you use it, you are at the 485 pending status. It will be safer to transfer to H4 if you don't want to work recently as long as your spouse's H1 visa is valid. Good luck.
We need to move on no matter how hard the life is. Cheer up.