BK, I think you are your own worst critic and I suspect that reviews will be be better than you imagine. Having been at the early reading, I can say the play's construction is solid, you play fair with the audience, the laughs are there, and all the twists are cleverly done. It is, in my opinion, the best mystery you've written and it works very well both as a thriller and as theatre. And, as I think directing may be the very best thing you do, I doubt that you've left anything to chance there and that the play covers all its bases neatly and smoothly with your usual polish and eye for detail.
It is tough to get laughs rolling when you have a third house full of critics, but they also can't be deaf to the intermission and after show buzz going on around them either. And just because they weren't laughing doesn't mean they weren't enjoying it or with it.
Like Fred Willard's wife, I think the play has the potential to be one of those solid regional theatre hits and get done everywhere. You might call Sam French and get someone from there to see it. It should definitely be published by them and, if it is put in their catalogue, it will get done all over the place for years to come. But, of course, it should have a helathy professional run first...and I think it will.