With 8 races to go, and McLaren pushed back into a clear 3rd position in terms of car performance,
Based on the last race, you are correct in that McLaren are 3rd right now. However, I wouldnt count on this being the case for long. What compromised McLaren is what happened in Silverstone - they couldve stuck with their new car to speed development. Instead they reverted back to their old car for the race, to ensure a stronger placing, for that race.
My belief is that they will be stronger (than in Germany), in Hungary and then will be on par with Ferrari in the race after that.
You are right though - if Hamilton were to have a DNF or a bad race, he could suddenly find himself in 2nd (or lower).