Belgium has some of (if not the) lowest income inequality in the OECD due to our very harsh income tax (highest median tax wedge of the OECD, yes even including the nordics). With quite a few asterisks attached to that statement of course because our fiscal system is a complete mess so if you're special kinds of well off (e.g. you make your income on capital gains) you'll be taxed very little.
How low income inequality doesn't correlate to very high standards of living like it does in the Nordics... Well I'll leave it to historians and economists to hash it out. The answer you get will almost certainly reflect that person's personal politics. Harsh industrial decline is worth mentioning though.

Wallonia is measurably poorer than Flanders, but both regions are developed western economies. The US has a murder rate 535 % of Belgium's, and I don't see anyone warning students away from studying there (or well, not until the past few months).
That judge should be investigated and the prosecutor should definitely appeal, and besides there is a lot of work to do safety-wise, especially for women to be able to feel safe, but that's hardly a problem specific to Leuven or Belgium.