If the landlord is making an addendum to the lease agreement, it is something you should sign of on. Or in other words, if your lease agreement states the late fee is 8% and doesn’t say anything about a $10 fee per day, then no your landlord can’t just change the rules. This is what is called an addendum to your lease agreement. Anytime there is a change it has to be signed and agreed upon by both parties. Its no different than you giving your landlord a notice that says you will be paying your landlord on the 15th, when the signed agreement says rent is due on the 1st. (It doesn’t work like that)
As for the cable… I don’t know what to tell you. I would suggest a complaint, if it is really bothering you.

Is it really a big deal?! Unless you are chronically late at paying your rent, what should it matter? Techincally, you can be evicted for being just one day late; so it sounds fair to me that the landlord is charging tenants a fee for being late per day.