Now they are saying closing on Monday the 16th?
I assume your boyfriend took two weeks off starting on Monday assuming the closing would be this coming Friday. If this is the case, I can't see how closing on Monday (and taking away 3 days from the 2 weeks you indended to work on the house ) can make that much of a difference in the general scheme of things if you still want to buy the house.
Seems both sides have had hiccups in establishing a firm closing date. This happens WAY too often for it to be a surprise.
Typically if the contract said closing "on or before a specific date" there is still a 10 day "grace period" before you can call the sellers out on a time is of the essence" closing demand.
Since you gave us some specifics, but not all of them and we are not attorneys, speak to your attorney ASAP, and get his/her advise on how to handle the situation to best protect you.
Take my word for it though, once you close you will forget all the aggravation that led to the closing and just focus on being a new homeowner. Good luck and let us know how it works out :)
The buyer usually has more power when things are close to the closing date than the seller does. More leverage. Unless the seller didn't really want to sell.