First you don't have to take 3 readings. Take one reading then another 2 days later. If they are the same then your good to go but most leave it another week.
Second there is nothing wrong with leaving the beer on the yeast for over a month. Many here have left it for several months for short aging or just because life got in the way... no problems.
Many in here dry hop in the primary (call it lazy if you want lol) In fact most I believe don't even bother with a secondary for most beers. Just leave it in primary for the extra time to clear up.