I'm a diyer, so take this for what's it's worth:
Regarding your first question...the relationship.
The 2 sec. vascillation of voltage on the O2 sensor between .2v and .9v and the 6.6v - 7.2v reading on pin 3(50 per cent duty cycle) to me are somewhat synonymous.
Not sure I understand the tail end of your 2nd question.
The final post in the following thread might be of interest if you're trouble-shooting a mixture control issue.
O2 sensor failure and lambda testing