The carpintis alone is just about maxing out a 75 gallon aquarium. Depending on exact species and sex, you're looking at a very aggressive and big fish that can be over a foot long.
You may be able to get away with a carpintis and one other compatible tankmate (salvini or convict may work) both of these fish are significantly smaller but can hold their own or take cover. Things could go the other way, and if you're carpintis is a serial killer like some of them are, he may not accept any tank mates.
I would not recommend a bichir for a central american tank. They just don't have the speed or strength to tolerate a big aggressive fish like your carpintis.... plus some of them get enormous. What species do you have?
Mollies and swordfins are absolutely out of the question with the current fish. They will get ripped apart or straight up swallowed whole. For dither fish, you'd need to go with something much larger and that would require a larger tank.
The bushy nose pleco will be alright for now, I'd assume once the carpintis gets bigger he may kill the pleco. I'd keep a BN pleco with a salvini or convict.
To accomplish what I think you want to do, I'd sadly have to suggest rehoming the carpintis. In a 75, a Salvani, convict, BN pleco, and maybe a school of something like giant danios would be nice. Giant danios are great dither fish as they are super active, are far too fast to be bullied and big enough to not get eaten (unless you have 10 inch+ fish then they are bite sized if caught)
Think about it and let us know if you have any questions with stocking or setting up the new tank. It's nice to see you upgrading. Your fish will appreciate a larger tank. Just when stocking always remember to take into account bio load as well as aggression. And always stock your tanks for the tank that you currently have.
