The Belgium revolt would never end up in a separate state if the Crown Prince, later King William II enter the city of Brussels together with his army and smashed the rioters and restored order, as the preliminary civil comity expected to do and wanted him to do.
To the astonishment of this comity of Brussels bourgeoisie the Crown prince halted his army outside Brussels and entered the city in friendly ambiance with the (French) agitators of the revolt and riots!!
This was for the members of the comity the, ''drop'' and wanted from then on full independence.
My opinion as posted earlier let this Crown Prince ( OTL William II) get this thing right or let him earlier be replaced by his more stable younger brother Frederick.
William I would have to make much concessions, to the Liberals, which would basically mean an earlier constitution as OTL 1848.
This will give the Liberals what they want and they would less and less support the Southern Catholics in their opposition against an Protestant King.
When the upcoming industrialization really went off the South will increase its influence over the whole Kingdom. Brussels would become the only seat of government and the Hague would drift toward obscurity.
Antwerp would become the 2nd largest port of the world before the end of the 19th century.
Most likely Ghana would not be sold.
Perhaps a son of William II (OTL) otl William III will be eager and greedy enough to dash in to an African adventure like the Congo.
OTL William III was an man greedy, eager and misbehaved as Leopold OTL. If he never become King due to his weak father he has a reason more to create his own kingdom and fortune. 19th Century Africa is a perfect place, he never have to visit it by the way.
The Royal house of the Netherlands was very close related to the Prussian Royal house early 19th century and there for far from hostile.
For overseas politics ( trade and colonies) the UK was seen as an natural Allie.
France was regarded, by almost all Europeans, as the aggressive State of the 19th century.