[Simple questions about creating a modpack]

- How would I add a resource pack into the modpack?

 

- I have custom resources in the resource folder, how can I add these to the modpack as well?

 

- And how could I do something similar to a "same world" like thing like seen in modpacks such as Crash Landing?

[Daytime Hostiles - Simply mobs spawn all the time!]

I'm trying to create a modpack that takes place in an apocalypse, but I don't really like how mobs only spawn at night except for one inside one of the mods (the mob aptly named "Day Zombie"). If possible, could someone make a small mod that allows all the other hostile mobs spawn during the day as well? Only at a reduced rate to stop swarming players?