I don't make my own mmf, lukcily our fondant here in Aus takes OK, so we don't really need to (I understand most of the US stuff takes rather blech)... but, oh boy, I understand where you are coming from!
I remember this one time I have some cupcakes to do for a store catalogue, and the deco just wasn't going right - I couldn't get this particular cake to look "right", and I was getting more and more p'od by the second, until bam! I just crushed that little sucker in my palm and threw it across the kitchen!
Felt great for a second or two, until I realised that I didn't have any extras! So my little tantrum cost me about another 3 hours work in rebaking for ONE lousy cupcake!!!! (Not to mention the cleaning oft the cupcake splatter from random spots around the kitchen! - SO glad you're much larger cake didn't splatter the way you wanted to, just for the cleaning up alone!!)
Lesson well learned! Now, if things aren't going right, I just walk away.
I know you wanted this cake to be right for your husband - and I'm sure next time, you'll ace it.