Questions on spousal visa

Hello, this is my first post on here and I am so happy I found this site!
I can't seem to find answers anywhere and the Embassy is £1.50 a minute!
My husband is from Florida and in the UK on a spousal visa. I have a few questions if anyone can help a answer the below questions, I'd be ever so grateful:
1) if we want to work on UK cruise ships together, like p&o UK,  does this violate his visa because he's not technically 'living' in the country?
2) his visa is up for renewal in June-how much does the extension cost?
3) if we don't extend his visa, we may get my greencard and try things in the states. If we hate it-can we reapply and come back to the UK again? 
Thank you so much! Cat x

As long as you were living together and the reason you aren't in the UK is because of work, it would be fine.  I imagine his address of residence would still be the UK.

Current fee is £649 for the visa and £500 for the NHS levy.  These will rise in April (annual increase).

What's an NHS levy?
We never paid that before?!

It's a new fee that was added this year. Everyone on a visa over 6 months get's to pay 200 GBP per year with your visa application fee as an NHS levy. So for 2.5 years it's a total of 500 GBP. If you poke around a bit you can get more information about it.

edit: here's a link for you
https://www.gov.uk/healthcare-immigration-application/when-you-need-to-pay