1. When I get my spouse visa for the UK, how many months does it last for?
It is valid for 33 months.
2. How many of those months must I physically be in the UK in order to keep it? For example, if I am gone 6 months out of the year back in the US (all at once or broken up) does my UK Spouse visa become void?
It won't become void, but you may not qualify to stay in the UK when it expires if it is not your primary residence and you are not living with your spouse continuously.
In order to qualify for ILR after 60 months (30 months on the spousal visa, 30 months on an FLR(M) visa), you have to prove that:
- The UK is your primary residence
- You and your spouse have lived together at the same address for the whole 5 years. If you will be in the UK 6 months per year, without your spouse, you may not be able to qualify for ILR... because you won't be able to prove you have been physically living in the same house as him all the time. If he were to go to the US with you for the 6 months, that may be okay, but then he would have to get a visa to live and work there too.
I know that I can come in to the UK without a visa for 6 months within a 12 month period as a tourist, but I want to work whilst I am in the UK so I will need a Spouse visa for this once married. I still want the flexibility of going back and forth to LA for my acting work so I'm just really trying to calculate it all out so that I don't jeopardise my position with the UK Border Office.
Well, you wouldn't be able to living in the UK as a visitor, because as you say, a) you cannot work, and also, b) you would be using the visitor visa to live in the UK without a proper work/residence visa... and that's abuse of visitor visa rules.
Each time you entered as a visitor, you would have to 're-apply' for a visitor visa, proving you had a return ticket to the US, a job, a home and a life to return to in the US, that you had no intention of living in the UK, no reason to stay in the UK, and enough money to support yourself without working while in the UK.
If you couldn't prove that each time, or if the immigration officer believed you weren't a regular tourist and were trying to 'live' in the UK, they could turn you away at the border and send you right back to the US.
3. (I will apply for Citizenship at the 5 year point)
Will I need to have this Visa for those entire 5 years in order to exit and enter the UK as I please? (I'm not sure what I need to do after getting the initial Visa) 
What you would need is:
- Spousal visa, valid 33 months, to live and work in the UK (current cost £851)
- FLR(M) visa, valid 30 months, to live and work in the UK (current cost £578 by post (but may take a few months for processing), or £953 in person, same day decision)
- ILR after 60 months of living in the UK on the above two visas (current cost £1,051 by post, but currently taking 3-4 months for processing, or £1,426 in person).
For each visa, you must show that you are still married, still living together in the UK, and still meet the financial requirement.
For ILR you will need to provide evidence that you have been living together at the same address for the whole 5 years - by way of providing mail addressed to you both at the same address, spread evenly over the qualifying period.
- Citizenship, once you have ILR (current cost about £870), but you cannot have been outside the UK for more than 270 days (9 months) in total in the previous 3 years, and no more than 90 days in the final 12 months before applying. So, you would have to restrict yourself to no more than 3 months outside the UK in year 5, and 6 months in total across years 3 and 4.
