How many DMs should I send per day?

I am using FollowLiker on a well-aged account. Does anybody know the safe settings for sending DMs? How many per day, at what interval, and how many variations of the same message?

It all depends.
Your accounts
Your message text
How spammy you are being
If posting a link, quality of (not your opinion of, but twitters)
Previous blocks on account / any twitter flagging of account

etc etc

In 2020, things are not as simple as "give me a one size fits all limit for X Y Z"

No one will be able to give you limits, these social media sites all have these “trust scores” and one report or action block and throw a curve ball into whatever you’re doing.