The "damage from uneven tyre wear" business is in the same category as using Nitrogen to inflate tyres - nice idea and theory but in reality is basically nonsense.
The whole point of "differentials" is to enable different wheels on the vehicle to rotate at different speeds - and there will be MUCH more variation being caused by any curves in the road (prolly even wandering within the lane!), the road surface itself - and even small differences between the pressures in all 4 tyres - than any effect from tyre wear.
You should definitely not use different types of tyres on the same vehicle unless its unavoidable and only for a short while, but differing wear isn't an issue in real life terms.
If you're anything like most people you have lots of things in your life that cause you stress - this shouldn't be one of them - it's not a problem so relax