![Cool 8)](./images/smilies/icon_cool.gif)
You are not being a fool...you are going about it in the right way by writing to each other for 5 months first up, and then taking the time to go and meet.
As for the age thing...you are not being foolish there either. The thai norm for age difference is around 10 years so 14 years is neither here or there....especially where you add the most important part of your text that being "we are both mature adults".
I think that when one is not in Thailand, and is first writting to a thai girl, then there is more chance that the main brain on top of the shoulders gets a chance to activate first and take over the lead role...result...a very high chance of a successful objective.
One comment I would make is treat yout time in Thailand as a first visit. Don't panic or worry about where you or her are likely to live at this stage. Just enjoy the time together in Udon and Thailand. I and others I know have trodden the same path you are taking. Generally the future will take care of itself and the two of you will start thinking about that once time left together in Udon surpasses time spent together. It is very normal for many falang/thai couples to commit to a life long relationship on this first visit but then spend considerable time apart. During that time apart that olde favorite "absence" kicks in and what seemed to be very difficult hurdles to overcome (where to live together) are a piece of pie.
My own partner who I thought would never leave Udon lives here in NZ. The 5 years only then return to Thailand has already been replaced with 10 years.