As I read the rules from the forum - the first / last seasons are dropped if they contain less than 400 AB - note from BBR. So you should be good with just the 2 seasons.
You must use the full player season in the year you are assigned.
First and last seasons of a player's career will be eliminated if they contain less than 400 AB, or less than 100 IP for a starting pitcher. This is according to baseball-reference.com, not ab/162 or ip/162. I do this because this is where I calculate the available seasons, etc. Starting pitcher determined by whether they have more appearances as a starter or reliever in their first or last season.