Are there any bass, catfish present in the pond from past stockings? Or does the pond just have BC from the past and the FHM and BG you recently stocked?

RES can be stocked and should be able to be sourced in Neb. There are several members here who are from that state who have them in their ponds... In an established pond, I would try to stock 75 6"+ adults to get them to take hold. If there are no larger 10"+ BC or LMB in your pond, more normal 3"-4" RES may be stocked at slightly higher numbers.

I'll let the feeding experts chime in on what you can do to get your BG to feed on pellets better. There are a number of methods you can use though.

BC can be difficult to manage, but they are not a death sentence. Generally an over abundant LMB population can keep them in check and lead to quality fish but there are many variables and things you too can do. Such as fishing and keeping all and as many as you can catch each year. Utilizing nets and traps to remove over abundant year classes, etc... Stocking FHM is just a 1 week snack in an established pond. Consider stocking larger sized golden shiners(GSH) and as you are doing, treat your BG well so they spawn and provide YOY as a food source.

Stocking the LMB and CC in the late summer or fall is not an issue IMO. I would try to get advanced sized LMB to stock if they will be competing with larger BC. 6"+ bass with 10"+ being better IMO. If you stock 10" fish, I would stock 45-60 LMB.

You can look into buffers around you pond to prevent runoff issues. Do a search of the forum as there are several excellent threads on here about that issue.