Literally nothing new today.
Waiters must be getting nervous 
I'm guessing OKC are waiting to see what happens with Westbrook. It can't drag out much longer before teams finalise moves to begin the season. I'm guessing it's about keeping cap flexibility
A lot of RFA's have to wait. It's nothing to do with Westbrook. It's daring another team to make an offer for Waiters only to lose him, which might not happen. Eventually Waiters will either sign for a reduced amount with OKC long-term, or play for the qualifying offer ~$6.8 mil, which is a bargain compared to what's been offered.
Right now the two sides are engaged in a staring contest. Same thing is true for Moe Harkless, and to a lesser extent Tyler Zeller.
Yeah you're right. I do think it's slightly more than that with Waiters though. If Westbrook is to be traded it's likely going to include an extension of some sorts which means the team he moves to needs the appropriate cap space. I think it's $8.8m for the upcoming season? If you traded him for equal salary then there is a very small pool of teams in play. However if they use their cap space to take on additional salary then there are more teams that can come into play. So I think that factors into the Waiters decision as well.
I think you've very much overthought this. If Waiters is moved in a sign-and-trade also involving Westbrook (I think that's what you were suggesting), Waiters' salary will count only half to the Thunder for what they're allowed to take back, and will count fully to the team taking him on. This will make it more difficult for a team to match salaries and wind up $8.8 million under the cap so as to extend Westbrook.
Waiters' negotiations has virtually nothing to do with Westbrook. The only way it matters is if Westbrook either demands that Waiters be a teammate, or that he no longer be one. Anything else is Waiters trying to get the most he can, and the Thunder trying to pay the least they can, and the staring contest that ensues.