Resipsa, this is serious stuff, baby-making at our age. Are these babies (whom we have yet to meet) more important than our marriages? Will our lives be okay if we don't have them? Are you going to be okay with just the one? Should our husbands move heaven and earth to try and give us what we want?
I suspect the answers to some of these questions may be different for all of us. My life would be pretty dire without my husband but when, after the miscarriage last year, we were failing to get pregnant month after month and AC was not on the horizon (and never would be due to financial constraints) I would regularly fantasize about running away and getting spectacularly knocked up by random strangers.
I regularly considered whether my marriage could sustain the weight of not having a baby in it, but when I look back now I can see that the question wasn't whether my marriage could survive with no baby but whether it could survive my aching obsession. Now that I am approaching IVF at full throttle I know the strength of what me and th'usband have in terms of love and commitment to each other and no way is a child who I have never met going to get in the way of that.
A failed IVF cycle will devastate us, but, at 42, I know we're done. I'm not destroyed by that thought: I squandered one baby years ago when I had an abortion and so I certainly don't feel that angst like I 'deserve' a child in the way that some women do. You've been together since 1997 so I won't ask you if you are 'in love' with your DH, but do you prize him still? Is he a Good Man? Does he adore your daughter? If the answer is 'yes' I think you're really, really lucky 
I think you've got a year to convince him to try donor eggs and secretly come up with the cash by yourself. But take that time to enjoy your lovely daughter and train your brain to accept an only child, then maybe no-one will get hurt in all this x