I think Gary makes a good point about fair weather investors and yet another good point about going non-consent. If there is the single well in the spacing, XTO needs to keep that well producing to retain that acreage for future use, something that would not concern you.
If the well is really costing you too much, you can probably deed your interest in that wellbore to the operator, I would certainly look into it if that would be attractive to you.
As for having signed the JOA, I can see where it could be attractive. It allows you to sit back and let the operator do the work and present you with a single bill. The thing is, you probably don't know for certain if that bill is accurate? If you didn't sign the JOA, you would have needed to supply your own insurance and write checks for every single thing the operator billed you for. Yes it's a pain writing several checks each month but then again, you know what it is supposed to be going for?
If there are other non-operating interests in the spacing, you could band together, sharing the cost and audit the operator. If there are other non-op interests, I'm sure they are no more happy than you are. Operators are notoriously bad about keeping records, I would refuse to pay for anything for which there is not an invoice.
It's never a good situation to be a guinea pig with a first well. I don't know anything about your well, whether there was an offset well that preceded yours but I have half a dozen wells in a half dozen different spacings that were drilled with 10 frack stages with "beach" sand in a really good area in McKenzie county and no more development in the 7-9 years since on my minerals, although there are about 10 permits in one of the spacings currently. It can be bad to be the first.
Some wells will cost more to operate and some are amazingly cheap to operate. It sounds to me like XTO is as I have heard people say before "Operating you to death". There are more ways to make money in oil and gas than simply producing.