Age isn’t a problem at all, you’re only 33...that’s young. You’re income is good for making a change if you can get rid of your debt and save for training. You’ll need to start living below your means and saving. The great thing is when you take the pay cut, you’ll be used to living on a reduced amount.
With a wife and 3 kids you need to be very methodical about how you do this. I agree that the slow route would be the way to go in your case.