I came to Germany in December 2005 on a dependant/spouse visa: Aufenthaltserlaubnis, § 30 AufenthG. There was a remark on that visa that "Erwerbstaetigkeit nur mit erlaubnis der Auslaenderbehoerde gestattet"

In September 2006, I got a job for which I was given a limited work permit and a new visa was issued. Everything else remained the same. Only the remark section on the visa changed to say that Employment allowed as Software developer only by the firma XYZ.The "Anmerkung" was still § 30 AufenthG.

In December 2006, My visa was changed again(Auslaenderbehoerde said this gives me a company independent job search permit since I was a dependant for 1 year) and this time, the remark section was changed to "Erwerbstaetigkeit gestattet". The anmerkung was still § 30 AufenthG.

My question is: Under the latest visa status, am I allowed to stay in Germany and work here independent of my husband's stay/work here? If my husband goes back to India, must I also return? Can I not continue to live and work here if he is not living or working here?

Pls. help. I need to take some urgent decisions based on this!

Yes you can.
You can even change firma without contacting AB.
or open your own company
or divorce