Flatteners and reducers

[SStanford]

Hi all,

With the ongoing stock shortage it's going to be sometime before I get my hands on my desired scope for my ideal setup.

I'd like to make the most of my current scope until stocks replenish and so I have a few questions about Flatteners and Reducers.

I currently have a Celestron Inspire 100az (details here), a Canon 450D and a EQ3 Pro (synscan).

As I understand, the 660mm focal length makes the scopes FOV too narrow for a mount such as the EQ3. Am I able to add a reducer to bring the focal length down to a level that would be suitable for this mount?

If so, can someone provide some guidance as to which reducer would be the right choice?

This brings me onto my next problem; I can achieve focus with my Canon 450D DSLR in the Celestron 100AZ but by only using the supplied diagonal (here) and my 2x Barlow (here).        

I have tried using the 68mm extension tube that came with the T-ring and adaptor (here), inserting this directly into the scope but cannot achieve focus at all. In addition to a reducer, what else do i need to add to the OTA to get focussed?

S.