1) Date filtering isn't supported yet, but probably will be in the next release. This one supports the following comparisons:
string: equals, contains, starts with, ends with
binary: equals, contains, starts with, ends with
boolean: equals
ID (such as a FID): equals
That was all I had time for in this release.
2) Yep, PFDAVAdmin will only show the folder-level permissions. The mailbox-level security can't be read through DAV. There are no plans to add that kind of reporting to PFDAVAdmin, so for now the solution would be to use some other tool to generate the mailbox security output, and maybe a script to combine the two sets of information.
That's an interesting idea about the custom forms reporting. I'll put it on the wish list. Thanks for the feedback, and I'm glad you've found the tool useful!