If the Design Checker times out, you can verify the form template on the
server using the command "stsadm -o verifyformtemplate".

There is probably something in the form template that is causing an
exception to occur during the upload. If you use "stsadm -o
uploadformtemplate" to upload the form template via the command line you
should be able to see the exception.

When we've run into upload exceptions in the past, the only way I've found
to narrow down the source of the problem is to remove views and/or controls
one by one until the form template uploads successfully.

To resolve your property promotion issue:
When a form template is uploaded via Central Administration and activated to
a site collection, Forms Services creates a site content type for the form
template. To get the promoted properties into your document library, add this
site content type to the library.