Big picture advice for new site with paypal, users, CRM, mailchimp integration

I just purchased the developer license and am playing around with the paypal integration and am liking what I see so far. But I want to do things right, so I am asking for big-picture guidance before I make anything too specialized and have to completely redo later.

I created a basic website for a non-profit that has had little to no web presence in the past. What they do is certify professionals and provide information to professionals and lay people. This is specifically what they want the website to do:

Accept payment for about 10 separate non-substantial items and one physical item that will be shipped (so far no downloads, just dues and fees, etc.). I need to tie those payments to the specific person, too.

Keep track of certified professionals: name, email, physical address, unique certification number, etc. Can gravity forms collect info to pass to another CRM besides mailchimp? I need a lot of custom field data that is not only changeable by the user but also by us (like for example if we want to change their certification status)

Keep a mailing list and send emails to certified professionals, those interested in becoming certified, and perhaps lay people in the future. I want to integrate with mailchimp. But I am concerned that I need a higher-power CRM than mailchimp (especially since mailchimp won't even store contact data without an email address)

Accept people's application documentation (word or pdf files they upload) associated with their unique account. It would be nice if these files were stored on the server, associated with their account. And they could edit their applications by uploading a new document. (am I aiming too high here? Or should I just have a form people can submit these with individually, that the secretary personally processes?)

I want to collect every interested person's email, whether they are certified with the organization or just interested in becoming so (as long as they explicitly opt in of course).

I want this all tightly functioning, of course. My biggest point is that I want gravity forms, mailchimp, and (hopefully) a CRM to integrate very nicely so our organization doesn't have people's information in ten different places, it all funnels nicely, and is easy to manage/export/analyze.

Any thoughts?

Thanks