Normally, I'd tell you Vegas is smarter than the public and if it looks too good it is, dont forget game 3, etc...
But the fact is in the NBA playoffs, they basically set the lines for the games in each city n stick with em (Pending injuries/suspensions, etc).. The fact that this line went from +9 in game 2 to +6.5 now in 7, only says vegas is moving towards the Bulls, so now Celts lovers might take that discounted price, and the Bulls may actually be the right side..
Personally, I love this as I am a die hard Bulls fan, and the only game I bet in this series was game 2 +9.. I will not be taking the Bulls tomorrow, but rooting insanely for the outright.
Best of luck to you and to the Bulls.