I am an F-1 student married a US citizen, applied for I-130. I wanted some suggestions/opinions/advice regarding my impasse that I am going to describe.

I am currently pursuing my PhD and will be graduating in Summer 2016, after that I want to apply for jobs in academia like lecturer or post doc positions. For this I may have to go outside the US and stay for more than 2 yrs. I just found out that if I am granted a green card, I can not reside outside the US or be absent for than a year. So I have the following questions

1. Should I postpone applying for the adjustment of status (I-485), since I don't know if I will get an academic job in the US. If I do stay in Europe for more than 2 yrs, my green card will be invalid and I will have to reapply again with all the fees etc. But then again, if I do get a job in the US and settle down, I won't be able to work without a work permit, so should I apply for a work permit instead?

2. Say I do go to Europe and after 2-3 yrs I get a permanent position in the US, I would want to come back and settle down, what kind of visa/entry permit will I need to enter the US?

3. If I am approved for the I-130, how long will it stay valid?

Thanks