In the city:
North Pond
Custom House
Magnolia Cafe
Sweets and Savories
MK
(We must have similar taste; you've already hit four of my top five casual fine dining places in the city, North Pond being the exception.)
In the suburbs:
Tallgrass in Lockport
Michael in Winnetka
Oceanique in Evanston
Chef's Station in Evanston
Vie in Western Springs
Le Titi de Paris in Arlington Heights
As for foie gras, Tallgrass, Michael, Chef's Station, and Vie have it, and probably Le Titi (haven't been there lately). Michael has the very best foie gras dish I've ever had - a medallion of seared foie gras over foie gras and mushroom strudel. Better yet, as I found out a week ago as a pleasant surprise, they're open for lunch on Fridays, and they have a deal, $35 for a three-course lunch, including anything on the menu - and the foie was one of the choices available for lunch that day.
You can also probably do
Everest for about your $300 limit, and significantly less if you're there for their pre-theater special, 3 courses for $50 at 5:00/5:30 every night they're open except Fridays. Speaking of deals, Custom House has a similar deal every night for $46. Oceanique has a similar deal every night except Saturdays for $42; if you go to Oceanique on a night other than Saturdays and you don't do this deal, you can use the $25 off coupon you'll find on their website.