回複：Option and time RE:OPT and NIW

The safest way is to file I539 to change to H4 before your OPT expires (that USCIS receives your applications before your OPT expires will be fine). It takes 3-5 months to get H4.
If you can find a employer to sponsor H1b before your OPT expires, you can change to H1. The question is when you can get a job. It takes 3-8 months to get H1b status after you get the job offer.
As soon as you file I485 with your spouse, you file for EAD. It take 2-3 months to get EAD. You can keep your non-immigrant status as long as you don't use EAD. You'd better not use EAD until your spouse's I140 is approved, which takes 6-24 months.