Switch from marriage based to employment based AOS

[agni]

I am currently on 5th year of my H1b and filed for marriage based AOS in September 08. I actually have the initial interview (I-485) scheduled for the first week of March 09. BUT my USC wife and I got separated after the filing and we'll most likely not attend the interview.
I have several questions in my mind but the critical ones are:
1)What happens after I have missed the interview (how does USCIS follow up?). Do they require the beneficiary to leave the country? In my case since I'm on an active H1b (valid till 02/10) I'm guessing I have no issues with staying in the country.
2) I haven't told my employer about this situation but they'll most likely agree to sponsor my green card when asked. How do I go about that in terms of canceling the I-130 and getting a I-140 filed?
3) Assuming my employment based AOS is filed, how many extensions of H1B can I get after exhausting the 6 years? What kind of time period should I be looking at?
Looking forward to get some answers and guidance from the senior members to help get me out of this pickle.
Thanks.

[txh1b]

1. If you are maintaioning other non-immigrant status, you will be fine. USCIS will deny the AOS and you can continue on the non-immigrant status.
2. The employer must have an approved labor before they can file the I140.
3. Labor should be filed 365 days prior to H1b expiry for one to be eligible for extensions. As an alternative, both labor and I140 should have been approved before the 6the year ends for one to get extensions of H1b. As long as the PD is not current, you can get 3 year extension with an approved I140 and 1 year with a pending labor or when PD is current.

[agni]

3. Labor should be filed 365 days prior to H1b expiry for one to be eligible for extensions. As an alternative, both labor and I140 should have been approved before the 6the year ends for one to get extensions of H1b. As long as the PD is not current, you can get 3 year extension with an approved I140 and 1 year with a pending labor or when PD is current.

Thanks a lot for your answers txh1b. I have a follow up question regarding the labor filing. My h1b expires on 2/3/10 (that'll be the end of 6th year) and seems like I'll be a few weeks short for the 365 day rule even if labor is filed ASAP. Is there a way out of this?
The alternative option (labor and I-140 b4 6th year) you stated seems unlikley to work me. Any other options? Please suggest.
Thanks.

[txh1b]

If you have spent any period outside US on vacations while on H1b, that period can be recaptured buying time for the 365 days of pending labor.

As an alternative, one could file for labor, take a long vacation if employer is okay with it, comebacj and recapture the period as well as age out labor to be eligible for extensions. Talk to your attorney.