OK so here is the rule for the OPKs. If it is *almost* positive... It is not positive, so i would not put a positive OPK on your chart. Also it is advised with OPKs that you dont test with FMU. I test at 10am and then again at 4pm when i am closer to O.
On the other question.... it really depends on the persons body on whether you have a dip or something else on your chart on the day of O.
The main thing is that you have 3 higher temps after O to confirm O.
take a look through the chart gallery on FF and see if you can see what other women went through with their O.
Good luck!!! and baby