Your logic about how much you are "spending" does seem to make sense. However, I would suggest putting the Delta flight on hold and then transferring. One main thing to keep in mind is that you need to register for the promotion and as a word of advice, make sure its showing in your promotions.
In terms of the two account merge, it may work to get you to 50K MQM, but keep in mind two things: 1- they did yank the extra MQMs from a similar promotion last year, and 2- this promo is also limited to first time transfers getting the extra RDM, and therefore you are risking losing that.
IMO, I would have one account for you, and one account for the wife, and put enough MR into each so that you'll have enough RDMs to fly, and leave well enough alone.
Good luck either way!