Is my presence in the US legal?

I agree with the others. You may have to go for H-4 visa stamping if the change of status is not approved

Can I change my employer before getting H1B visa stamped, will I be considered cap exempt?

is an employer willing to sponsor you? it will be up to their attorney

What is my current status? should i file h4-ext? how long can I stay in usa? what actions should i take? plz suggest

H-4 until Your husband is denied When does the I-94 expire ?

Your passport should be all you need unless you or your spouse have been married before. Then you need divorce certificate

Can one apply for the US Spouse Visa from a country that is not the US or the spouse's home country?

Yes it is possible if you show you are residents of Japan . I would contact the embassy there

Can I do the my medical exam for my i485 form now before the i140 approved?

An online forum is not the best place to 2nd guess your lawyer. Medicals submitted to USCIS are only good for a year. Thee is debate whether it...

What's is next for my case? am i getting a new extension letter, or what should i do from this point?

sounds like they are investigating the bona fides or you marriage and your case. i would do an infopass or hire an attorney to inquire

there is no official time frame they will get to it when they please . Try calling them but do not expect a response for many months

My Visa Amendment and I140 Approval status

It can take 6 months or more for the I-140 to get approved. In my opinion you can file the extension now too. You may consider upgrading to premium...

Can parents of my spouse Co-Sponsor me?

Yes, it is possible as long as they are citizens or green card holders and make enough income