It is all in your mind!
Rizq is from Allah and not from your employer or from your wife to be.
People look at your age an performance and not on the whiteness of your hear.
Have confidence in Allah and put your full trust in Him as these fears are from Satan. Nowadays, people dye their hair with white stripes as a new look and a form of fashion.
You can always dye your hair, providing that you avoid black color. You can dye it s with a mixture of black and brown so that it looks dark brown.