Hello Stephen D, No you are not being paranoid. Once bitten twice shy.
Experience is a blunt teacher, AND you only had a bad fright and NO injury. Fortunatly a relatively low cost learning experience.
You ALWAYS have several things coming togather to cause an accident.
In this case, in a hurry, not looking,ran over a heap of dirt, NARROW track(width).
This combination WILL arise in the future so you need to break the incident chain.
Practically, this means increasing the track(width) of the tractor so an abrupt shift of the centre-of-gravity does not tip the tractor over.To do this with your existing rims you have 2 options
1) get wheel spacers, steel or aluminium. These are low cost and you will be surprised how a small increase in track has a large increase in stable "feel". Other members will tell you what they use and where to find them.
2) Dual wheels, massive difference in stable "feel" a much larger width (can you fit every where you currrently go?) Generally you will slide of the hillside instead of roll off the hillside. In your case backing over a heap of dirt,you better have your seat belt on as you are likely to be tossed into the door instead off rolling the tractor.
NOTE :
1)Your stability comes from the back axle. Making it wider gains stability. The front axle is on a pivot and by the time it hits the travel stop you are past the point of no return.
2) In your photo you have the loader down low. EXCELLENT, that is where it should be(curl bucket right back so if you hit the ground it slides instead of digging in). And when you are loading a trailer etc, keep the loader low UNTIL you are approaching the trailer to tip into it. A common mistake is to lift up high WHILE MANUVERING. This is a classic roll over senario.
3)
Ballast: Are your rear tyre filled (partly) with liquid?
You will find a 3ph couterweight to be a good safty invest ment. Ask other members how they made/setup theirs to see what would work best for you.
4)Is there a company that does tractor saftey near you? Possibly state Ag saftey? Some formal trainig may be the best way for you to grow your confidence back.
Some food for thought.
Good Luck.