No, don't apologize. But for the future, do learn to spell out in your contract the kind of response time you expect from your own client.
In your case, you clearly communicated that you were not going to be available. In the case of your client, he didn't communicate anything to you, so you have no idea if that person took an extended vacation in advance of Thanksgiving, or if that person had a heart attack, or if he's giving you the silent treatment, or if he gave up on you entirely after you reminded him you were going to be unavailable.
That is completely unacceptable. Remote contracting is difficult as it is. It needs to have clear rules of communications between both the contractor and the client, that both parties need to abide by.
Also, you need to have a contingency plan in place in case a client abandons you midway through a project, or if the client doesn't have the time to talk to you, or changes the project to something else entirely, or if a client doesn't pay you.
By the way, it does sound like there is some uncertainty about getting paid for this contract. Having not planned for that contingency, I still think you should finish the work even if you don't hear from him, but that's just my opinion. Ultimately, you know more about the situation than I do. If the work requires his feedback, then you're stuck I suppose. Or if you really believe in your gut that the client has abandoned you and won't be paying you, you might as well pause your project now (assuming it doesn't hurt your chances of suing him and assuming you would be willing to sue if it came to that).
But either way, if what you said is accurate, do not apologize. An apology will train your client to treat you unprofessionally anytime he wants and get away with it. Also, an apology may be used against you if you do try to sue for payment, so be careful about what you say to him.