The whole purpose is to unwind and get a breather from your daily work

They say that, but the reality of it is that its just enough time for a smoke break, and some time in the bathroom before you head back to work. Maybe shove some food down your throat without chewing it. You can learn to "unwind", maybe even take a quick nap with practice, but those things are not the purpose of the break.

My managers are like hawks on taking a 15, will be radioing you or coming into break room to check on how much longer you have left and often accuse of you of going over

That just sounds like they are being intentionally abusive. Now if you are on a timed unpaid break then you must be relieved of all duties for the duration of that break otherwise it is not unpaid. If they fuck with your unpaid breaks and expect you to get back to work during them then you may have legal recourse for that.

Past that, you can try to tell them to stop bothering you and that you have a timer going for when the break ends. If they start going on about nonsense like "time theft" can also make a point that you dont appreciate them stealing your time during breaks.

I have to ask permission when to take my daily break , when to use the restroom . It’s slowly killing me . What type of jobs out there give longer breaks ?

I get that needing to ask for the breaks, but needing permission to go to the bathroom is a bit much. Just tell them you are going to the bathroom. They cant really do anything about it directly. They deny you restroom access when "asking for permission"? https://www.osha.gov/restrooms-sanitation

"Employers must:"

1. Allow workers to leave their work locations to use a restroom when needed.
2. Provide an adequate number of restrooms for the size of the workforce to prevent long lines.
3. Avoid imposing unreasonable restrictions on restroom use.
4. Ensure restrictions, such as locking doors or requiring workers to sign out a key, do not cause extended delays

Though in all fairness id try to find some other place to work with, or otherwise start keeping detailed records of every time they disrupt your breaks, why they did so, any time they deny you access to the bathroom, and any other abuses you may be experiencing. Tons of shit in your post that involve potential red flags for illegal practices by your employer, and if they retaliate against you for advocating for your self then you may have legal recourse. Even if nothing else such efforts can help you later if you quit due to their hostility as it can serve to prove that you were forced to quit due to constructive dismissal practices.... something which leaves you eligible for Unemployment benefits.