So this is short any choppy cause I’m on my phone.
Not every amendment (or right/power in the main body) is negative. Article I Section Eight is a full list of powers allowed to Congress - those aren’t negative rights.
NFL business owners can limit speech because they’re the ones who ‘own’ the property, who make the employment contract. As you say, freedom of speech is, by the amendment, a limit on Congress. Employers can go through your locker because they own it - but your employer can’t search your house or go through your car willy-nilly unless you give them permission to.
However, some of the amendments aren’t limits on Congress - Four through Eight deal mostly with the courts and civil/criminal legal processes. How many federal courts do you think were involved in suits of less than $20? So why would the Constitution even mention stuff that was going to be a state/County level court process? These amendments didn’t need to be incorporated against the states, they were, by their wording, a universal right retained by the people. The Second is the same - the right of the people shall not be infringed. None of the wording in the amendment itself or the preamble states it is limited to Congress. The wording within the amendment, too, entirely applies to the people, not to the government.
...The wording within the amendment, too, entirely applies to the people, not to the government...
“[A] bill of rights is what the people are entitled to against every government on earth, general or particular, and what no just government should refuse.”
- Thomas Jefferson, December 20, 1787