Hi Bob,
Welcome to the forum, to answer some of your question in part, I highly recommend this site:
https://astronomy.tools/calculators/field_of_view/
It allows you to plug in various combinations & see what the results will be, including sampling rate.
You will not need a focal reducer for imaging planets, in fact, you might want to employ a 2 or 3x barlow. For the moon, reducer is handy if you want to capture more of the moon than just a small segment.
If you decide to purchase a focal reducer, don't buy the 0.5x they aren't particularly good & really aren't suited to an SCT. If anything, you want to get an f6.3 reducer designed specifically for your SCT, both Meade & Celestron have one, either one will work; make sure you don't get the Edge HD one if buying a Celestron one.. it's designed specifically for the Edge HD.
Depending on what you want to do, there are other options for a dedicated camera that are less expensive. I use a 224MC for planetary work & a DSLR for deep sky... The 224MC has a very small chip, works well for planets but, cannot capture a full disc moon, from memory, even with a reducer. Somne folk swear by the 290mc, slightly bigger chip but, not by much. Plugging in the different cameras in the link I sent you, the 178 & 183 will not get you full disc either, however they will get you more of it.
T-ring for your Olympus, I believe this is what you are after:
https://www.opticscentral.com.au/t-m...U#.XzCDU5MzZgc
Together with one of these from Sirius optics.. you can adjust the spacings with this rather than a fixed length one:
http://www.sirius-optics.com.au/siri...SABEgJjyPD_BwE
Hope this helps...