As you've signed up to a fixed term deal that ends in 2013, my feeling is that you will find it a lot easier to move if you can hang on until after that deal has ended before selling.
Porting a mortgage means that you transfer the mortgage onto another property without any penalty to be paid. In this case there would be no penalty what so ever as the contract has not been broken, just transferred to another property......Saying that, if you are significantly reducing your mortgage value due to this move the penalty may be applicable in some form and Halifax will insist that this is paid upfront before any new mortgage or port can be completed
The first question that needs to be asked here is are the problems with the existing application with Halifax due to adverse credit or affordability? You have mentioned that the payslip etc is confusing but you have also suggested that your credit may not be sufficient to pass the application, you suggest it may not even be sufficient to gain a rental property.
I don't really have too much that can help you in this case, if the application has gone to appeal then it is purely up to Halifax how they proceed but I have found to my cost with several applications to Halifax that most appeals remain in decline. You may be able to ask them to approach your husbands employer for an employment reference which might better detail his income but if it comes down to any adverse credit or blips on your credit file then it will most likely be underwriter discretion and there is not alot you can do to sway the decision your way.
There are other lenders out there that will allow a little more adverse credit than Halifax but you will then definitely need to pay the Early Repayment Charge then (probably around 2% of the mortgage balance) but you have to understand that if you cannot be taken on by a high street lender then to be accepted by a non main stream lender will more than likely mean that you are going to take a far higher interest rate for the risk on your application and you have to ask if will this work out to your advantage or just put you in the same position with a smaller debt but the same mortgage payment and different company name.
I would suggest to Halifax that they apply for an employers reference to help clear up the income debate. If this does not help then speak to an independant mortgage broker as they will look at your circumstances and know better where to place you for your mortgage. I would not advise to speak to any bank adviser (they are mainly just monkeys dressed in suits and rarely qualified and certainly not allowed to give advice) as they will only push you onto their own products without fully assessing your position....they are paid to get as many applications as they can into the bank, not to get them passed and completed.