For the issue with Anthony. It sounds kind of like you might be getting the 5th Event prenotification over and over: "
Sup, $n? Haven't seen you in a while. Why don't you come over sometime?" But the event doesn't trigger because you already went through the dating events with Anthony? I don't actually see that line you mentioned, so I'm not exactly sure where you are. I think you did the GetBackTogether event from his journal. I'm wondering if maybe the star change for Anthony was a mistake and it caused the issue there. The other characters GetBackTogether events don't change the star count like that, so I'm leaning towards that being the bug. If you email your save to support @ verdantskies.com, I can take a look and maybe get more details.
For modding, make sure to check out the base content and modding resources here:
http://verdantskies.com/modding-resources/
and the wiki:
https://verdantskies.gamepedia.com/Creating_mods
For adding new characters, the Marina Expansion mod by MidnightMasquerade is a awesome example of someone with a lot of events. If you're adding an entirely new character, there are some limits. You can't use the modding system to add a house for them, for example. That means they won't have a crib or journal. So you might want to consider a mod that reworks an existing character if you want the full depth. (You can replace their artwork, change their display name, etc).
You don't need the steam workshop to make mods work. You should be able to use the local modding folder for your own mods just like you presumably are for Marina. If you want to mail me your mod, I can take a look at what might be wrong.
Thanks!
-Andy