First - every story has two sides. I have done my best to imagine what the other side might be in this case, but for the most part, I am assuming that everything the OP has written is, in fact, true. Given the statements he made, I think the following:

1. The OP did nothing wrong by requesting an upgrade in advance.
2. The OP can communicate with the property as much as he would like in advance of his stay - especially if it involves the potential purchase of additional goods/services from said property.

(Why he's being attacked for the first two items by some here is beyond me).

3. Was he right to go to the Corporate line when his room wasn't ready upon check in? This one is a bit up in the air for me. I suppose it depends if he was trying to check in early. If he wasn't, then the answer is easy - no. A room should have been ready (upgraded or not). If he was complaining that an upgraded room was not ready, then that's a different story.

If he WAS trying to check in early, AND he had explained calmly the nature of his need to check into a room to both the person checking him in AND the manager, then I don't think escalation to corporate was a problem. After all, if I was desperate for a shower/change of clothes before an important meeting, I would try everything I could to make that happen.

Did the manager necessarily lie in stating a room was not available? No. It could have been that a room WAS available for a shower and change scenario, but not available to give to the OP for the whole night/stay.

It all comes down to clear communication. What the OP REALLY needed was a room in order to quickly shower/change/freshen up. Neither the OP nor the manager was able to determine the actual NEEDS and come up with a creative solution that solved both problems. I don't think the OP can be fully blamed for this, as he was clearly quite stressed about his meeting and focused on the requisite shower/change of clothes. The manager should have done a better job investigating what the problem was and presenting the OP with all the options that were available to him. The OP does not manage hotels for a living and might not be aware of the intricacies of room inventory management/cleaning schedules/etc.

If this had happened up-front, there would be no need to "pull rank" and call corporate. It should be noted that it sounds like corporate did exactly what I described above.

4. Was the manager right to scold the OP for calling the corporate line? I say no to this. A manager of a hotel is expected to act in a professional manner at all times when on duty. A hotel guest, is not. Nothing about this conversation was professional. Can the manager be pissed that someone went over his head? Yeah! Absolutely. I would be! - but to fault the guest (in direct confrontation) for that is uncalled for and unprofessional. Was the OP acting unprofessionally in his dealings with the hotel? Maybe/possibly, but that shouldn't matter. The management should be the "bigger person" in this type of interaction. If management acted this way toward every Marriott customer that was rude/inconsiderate/unprofessional, it would be a VERY unpleasant place to stay.

5. Should the manager have shared details of the interaction with OP with his superiors/colleagues?

Well I suppose the better question is, for what purpose did the manager share these details? I can't imagine there was any purpose served other than to damage the OP's relationship with his organization or perhaps to make some preemptive attack in case the OP decided to complain to his group about the hotel's treatment of the situation. I can't really come up with a good reason for the manager to have done this. Are there possibly situations that might warrant such a disclosure? I think there are. Was this one of them? I don't think it was. I think this is more unprofessional behavior on behalf of the management.