Hi springerandy,
When importing a DWG for use as a title block, as you've found, it can't contain a number of unsupported (in Fusion) objects (like xrefs). When you Output a DWG from Fusion drawings it contains all of the objects in the drawing so this won't work for re-import.
The Fusion Drawings template (f2t), while it can be downloaded, can't be accessed by Fusion for new drawings if it's on your local machine, you'd need to re-upload it.
The best way to handle this is by saving a Fusion Drawing template then using that when creating new drawings. If you have a drawing set up with the title block you want, my recommendation would be:
1. Open the drawing with the desired title block
2. File > Save As
3. Select Drawing Template (*.f2t) as the format
4. You can now open this template, make additional edits, etc. as required
Now when you create a new drawing, you can browse to and specify this template instead of using the default "From scratch" option.
Once this template is created you can also access it to add new sheets to an existing drawing:
1. Open the existing drawing
2. Right-click the sheet thumbnail in the sheet bar at the bottom > Add Sheet
3. Expand the "From" drop-down and select your template instead of the default "Current Drawing"
Now a new sheet will be added containing your title block. This also adds the block definition to the drawing, so if you switch to a different sheet, you'll be able to select this title block in the Sheet Settings (at the bottom of the drawing window) > Title Block menu.
This thread: Custom Title Block and old drawings also contains some more info on the subject.
Hope this clears things up a bit. It can get a bit confusing, please let me know how it goes.
Thanks,
Chris