Haha yeah, i didn't mean to come across that harshly (although it probably did come across like that).
I suppose at the end of the day, if you can do the challenge again later in the same time, with better form, you know you have improved. Or likewise, in a better time, with the same form. And thats all that matters.
Its pretty obvious from your video that you got a very hard workout done in 5-6 minutes.
I had a go recently and was just under 10 minutes, my form did suffer too towards the end. I didn't video but i know that my pushups were taking a good 2 seconds each in the last 40 or so reps (my chest hit the ground so many times..) and were definately the hardest part of the burpee for me. I had no troubles jumping 18" .