I go to the stadium a lot less now (too).
"too" would not be used with this sentence by itself. There would need to be a previous phrase, for example:
I go to the city a lot less now, and I go to the stadium a lot less now too.
Now if we substitute the meaning you asked about:
I go to the city a lot less now. Now also, I go to the stadium very rarely.
Basically it is OK, but "a lot less" means "a lot less than before". It could have been 200 days/year before and now it is 50 days/year.
However, "very rarely" is "hardly at all", and should be a very small number in any case.
"a lot" here is used adverbially. It can mean to a great extent or frequently.
lot
adverb (preceded by a)
13. to a considerable extent, degree, or amount; very much: to delay a lot.
14. a great deal of the time or often: to sing madrigals a lot.
Collins English Dictionary
1.a lot or lots (Informal)
b. Used adverbially to mean "to a great degree or extent" or "frequently": felt a lot better; ran lots faster;
doesn't go out a whole lot; has seen her lots lately.
American
Heritage Dictionary
That Amazon page lists statements that supposedly apply to leaders.
One of them is:
Are Right, A Lot
Leaders are right a lot.
What they are saying is:
leaders are very often right
In an informal way.
To answer your question
Can one say "John is right a lot..."?
You can, for example:
John is right a lot in his decisions.
But this sounds terrible as a sentence in my opinion.
A better way to say something like this might be:
John very often makes the right decisions.
They've just chosen a quite informal way of saying leaders are very often right.
The word "lot" has many different functions and forms. Usually "a lot" and "lots" act as adverbs, while "a lot of" and "lots of" act as quantifiers, a type of determiner, that is, they tell you a quantity, much like "many", "few", "some" etc.
There are some good sources on the internet about the use of these variants.
Best Answer
Yes, this is a colloquial use of "mad" as an intensifier, like "I've got mad skills" or "the boss level is mad hard" (see definition 9 in this entry). Don't be confused, there's also a phrase "mad money" meaning "money to be spent however you want," but that's not the meaning that's being used here.