Well there ya go ask a question and get a bunch of different answers.
In my opinion you have done the right thing. By opening the choke you have made the gun more useable and more sellable if you choose to go that way.
There is nothing wrong with Browning barrels made in Belgium but they were never meant for steel, in fact as someone else mentioned the fixed choke Japanese barrels aren't meant for steel either. The main problem being the choke constrictions. Modern guns have screw chokes made from hardened steel that can take the pounding of steel shot, but the steel constrictions are different, ie a lead modified constriction is approximately the same as a steel full choke. Another option would have been to have the barrel screw choked by a competent gunsmith .
As you can see there are many fans of the old humpback and if you get the right buyer for a vintage A5 in the condition of yours you could get over $1000 for it, the whols issue is finding the right buyer, Guys who tell you 400-500 simply aren't interested in this type of gun and don't see the value that a collector might. On the other hand you might have to wait a while, or sell it south of the border.