It's an unfortunate and difficult position you are in Eagle, I really feel for you.
I wouldn't think of it as 'giving up', I see it as a decision for your own wellbeing. If you're not in the position to move on from the company at the moment then by accepting that as it is, your decision is to carry on professionally advising (and influencing) the company to the best of your ability in the circumstances.
It sounds like you're doing the right things and trying to affect behaviours and attitudes for the better. I'm guessing that although you might be having a bit of a 'wobble' just now, your determination won't change and you will keep at it because it's the right thing to do. I believe that when people see you decide to fight the good fight and keep on going, they might not show they are listening and changing but they will be inside and don't want to shout from the rooftops about it. If they did, they might feel it could affect them negatively in their peer groups. It will start to change though, slowly, but it will.
I agree with everybody else above, keeping records is vital. One thing I'd encourage you to do would be to inform your top management formally of the legal position they will be in if they don't accept and act on the advice they are given, making sure to get 'read receipt' proof. As safety professionals we must close that loop and give management the final decision of accepting or ignoring their responsibilities. If we don't do that then we run the risk of not giving impartial and complete advice; if top management plead ignorance, obviously not a defence but it happens, then they will be left saying you didn't tell them...they didn't get your email...they're busy people, don't have time to read every single thing...etc. Give them all a person needs to make an informed decision and let them make theirs.
It might feel a bit of a lost cause or you might feel a bit helpless at times, but if we don't do these things our profession demands of us then it could mean change doesn't start to happen today, even if it's just a tiny drop in the ocean.
Our gang is bigger than their gang by the way
We're all here for you.