To say he was wealthy is completely unfounded in scripture. Just because he was a descendant of David does not mean he was rich. David was 28 generations back from Jesus. Him being Davids descendant does not mean He had a lot of money. Why do you have so much problem with the idea that Christ could have been poor? It is really a matter that is inconsequential. It does not change the gospel, and it is not mentioned in the gospel either way. There is nothing wrong with portraying Him as coming from a humble beginning.
Now, you say that it was used as an evangelization tool. You are going to have to show some saints that used this as their tool to evangelize because I have not read one saint that has. To say that people converted because Jesus was poor is absurd, people converted because He died for their sins and they found it to be true.
Now, for the Holy Days. No, they were not created for the purpose of covering over the pagan holidays. They were celebrated to honor Christ. Easter, or the pasch, has been celebrated as a remembrance of the Passion and ressurection of Christ. Now, they might have chose a final date due to pagan holidays to allow the pagans who were converting to have some sort of celebration around that time to make it easier on them for conversion. It was not for assymilation of their faiths.