Thank you for your Question.
Yes, Islam asks us to respect our Parents and be polite and soft when dealing with them.
But it also emphasis on How we should be able to help them when they go wrong.
You have been trying good.
I would suggest,
-When you’re trying to put a word across make sure you have a normal tone to your speech.
A different tone may ring different bells.
-Keep the same tone through out the talk so that it doesn’t provoke unnecessary argument between the two of you.
- If you have already argued several times over a same topic. It’s best to let it be until maybe some time later in life. Because the idea you’re trying to send across is already registered in his mind and he doesn’t want to comply with it. (It’s OK for this to happen. We should give him some room and breathe and then maybe touch base once more)
- I don’t know how practical this can be in your house, it will highly depend on your Fathers temperament.
You can reverse one of his good actions and show him how others can think negative of it.
This may make him realize that he maybe doing the same!
I hope this helps.