(SOLVED) How can I make a dimension that is always daytime, doesn't spawn any histile mobs?

For your first question with making it always day, you will need to lock the code for your dimension and then open the dimension_type > DIMENSION_ID.json add in a line for "fixed_time": and then your number. The number would be the same number as in they /timeset command in the base game - https://imgur.com/SIpd2YY

For your second question, there shouldn't be any entities spawning in your dimension by default, you get full control of what spawns in your dimension. Under the biome creation, there is an option for entity spawning, and you can just clear that list out.

If you are experiencing issues with mobs still spawning, you can create a blank procedure with the "Entity Spawns" trigger, 

if [ID (event/target entity) is in = your DIMENSION ID] do despawn [event/target entity]

You can also create some further "if" conditions before de-spawning, like "if entity = hostile mob" do "de-spawn"

No problem! Happy to help :)