I was wondering what it would require for us to move back to the UK? Would I have to show proof that I could support him financially like he had to do to get my green card (eg, Would I have to provide wage slips etc)
Well, you as a couple would have to be able to support yourselves as a family. You will need to provide proof of what both of you are earning, wage slips, etc. You also would have to prove your abilty to find work, so his CV and your CV plus work history. It would be easier if one or both of you had a job offer in the UK. Also, if you have family or friends that would allow you to move in with them or help support your financially or both, then that can also help.
One thing many couples do do if they can afford it is that the UKC will return to the UK to re-establish residency, find a flat, a job etc and then the spouse will follow a short time later. It means less you might need to involve other people in proving you have a place to live in the UK. I am sure with a child on the way, that it might be too much of a burden to work all that out and be apart, unless you have a great family support system in the UK.
What is the minimum amount I would have to have to prove that I could financially support him, and would we be able to use savings etc for this?
Savings is a factor, and you should include your information. They are going to look at you as a couple being able to support each other. There are no minimum amounts, it is all very subjective I am afraid. The entry clearence officer is going to look at your situation and say "are they people going to end up on the dole?" If the answer is yes, they are going to make you go through a more formal interview process and require more information of support. But again, if you are living comfortably now, you hopefully will be acceptable to the UK.
How long does it take to get him a spousal visa? Would he be able to work immediately upon our return?
If you apply in person (Chicago, New York, Los Angeles), if your application is fairly routine (and in the US about 90% are considered fairly routine) then you would get your entry clearence visa the same day. If you do it by post, it is about 2-3 weeks turnaround. You can apply for everything online (different then the IND website) at
http://www.visa4uk.fco.gov.uk/. It will also detail all the supporting documentation you need.
Essentially he would be able to work immediately upon return. The one thing I don't know off hand is if you have to convert your entry clearence to an IRL right away, or if that is all taken care of before entering the country. Hopefully Victoria or someone else can help clarify. But either way, it would be just a matter of a day or a couple weeks depending on if you did it in person or by post.
Also, how long have you been married? If you have been married for greater than 2 years the process as a whole is a little easier, because they will assume you are going to be staying together for quite a while. Also, if I am not mistaken, you can basically directly apply for an IRL (UK equivilent of a US Green Card).
Budgeting is a bit more difficult. How difficult do you think it would be for your husband to find work? He will not be able to apply for any civil service jobs until he gets his UK passport (which would be three years from entering the country). You are going to spend a greater percentage of your money on housing then in the US, that is for sure. Your effective tax rate may be a little bit higher in the UK, but that depends on a lot of different factors.
Also, realize because of your British citzenship and your Husband's American citizenship, your child will have the right to both US and UK citizenship no matter where he/she is born. Of course one your child is born, your are going to have to get a passport for them and apply for them as a dependant when moving back to the UK. While there are no issues with it, it just means more paperwork!
One other thing is that your husband and yourself will both still have to file US tax returns. If you do not earn over $80,000 per year you won't have any taxes to pay. After a couple of years (and I can't remember how long exactly) you won't have to file any longer, but your husband will always have to (the price of being an American).
