In my usage of the mod, it doesn't seem to want to put down curved train tracks. Is this possible to fix, or is there something weird with how curved train tracks work that prevents it from working with this mod?

I think at one point rail was working. I’ll have to check on my side and see, but At one point I was trying to fix placement of certain special modded entities and I thought i ended up fixing rails as a side effect, but never figured out the modded issue. Either I misremembered, rails never worked. Or something broke it with a game patch. Or I never updated the mod to include the update.

Are you on 0.16? Or 0.17?

On 1.0 it places curved tracks, but it does so even when I have only 1 track in inventory, essentially quadrupling that amount.

I won't have time to correct this, if it is an exploit. If someone wants to contribute a fix and can list the code update required, I'll be happy to update it on the mod portal for everyone.