You should consider testing these ideas with an automation tool (such as BF Bot Manager or Fairbot) that way you can test (in sim mode) loads of matches without having to do so manually
If I could make a suggestion, you should record the starting prices as you mentioned but I would suggest also recording whether it's a men's or women's match. I suspect both players trading down around 1.5 at some point during a match happens a lot more in women's matches.
How are you judging what the lowest odds are? It looks like you are just getting the lowest its ever been offered at (Pre off and IP). If that is the case then none of your data is valid. Any Lay the field strategy uses the move from SP to lowest IP. Your spreadsheets look good but its not valid data. You ignore so many important things like liquidity, position of your money in the book etc. Unless you are actually trading these on betfair you really dont have anything.
Hey man, I was keeping track on the lowest odds after the start of the match, I wasn't including any data from pre-match, I also had each match sorted by a minimum liability of £1,000 to ensure it would have enough for the stakes I like to use :)
The data is valid, all we want to see is when laying the court came in. And if there's anything to be summarised from it before going any further with any other information that may be useful, no point hardcore data mining if the ''basic'' part of the strategy doesn't show profit.