Danielle, you two are going through the scariest part of the process right now. You've already taken the necessary actions that are actually under your control and now have some professionals looking after your man, who is very lucky to have you looking after him. It's very tough not to spend a lot of time worrying, but worrying does nothing to benefit him. Easier said than done, but I tried very hard to realize that others (who are all professionals that know a lot more about this than I did) are working hard on my behalf. The surgery is coming. They're going to remove all of that nasty stuff and take the steps needed to fix him up.
I'll skip the detailed bits about the surgery, additional treatments (e.g. radiation) and recovery that I've posted about on other threads and get right to the good news. If you want to do some reading to know in great detail what to expect, check out some of the posts from other users like CherylD. From my own experience and that of a few others in these forums, I'd suggest that it is very likely that in time, he will be able to return to his duties as a project manager and still be able to speak reasonably clearly - enough to be easily understood and still be effective at his career. The process will take awhile. Several months, most likely, but it gets better! I'm told by others that they can understand almost everything I say. Occasionally I have a tough time with certain words or letters. Worst case, I just spell it out with the phoenetic alphabet (you know - Alpha Bravo Charlie, etc). If I have to speak a lot my tongue tires, so have to drink some water and then I'm more easily understood once again.