] 2) A man of Mr Darcy consequence, wealth and taste, which painter would have chosen for having made his portrait?

I can give you a suggestion for who it's not. Thomas Gainsborough is a famous portrait painter, who painted people of Darcy's wealth, taste and consequence, but there are 2 possible reasons why he may not be Darcy's portrait artist in this instance;

1. It's possible that Darcy's portrait is too late. Someone will want to clarify me on this, but one of Gainsborough's most famous portraits, "Mr & Mrs Andrews", was painted circa 1750. Depending on when P&P is supposedly set, Darcy's portrait would have been painted up to 60 years after that - Gainsborough would have been an old man by then.

2. Still using "Mr & Mrs Andrews" as an example, he sometimes (not always) painted in the picturesque scenery along with the portait - from memory, Darcy's portrait has a dark background only, with maybe a hint of a scenery. I could be mistaken, though.