The two week wait is in force because lets be honest, you aren't going to make the necessary fitness gains in a week, or arguably two. I am baffled by pjft failure though. I had never actually ran a timed 1.5 mi until the day of my pjft. I honestly don't recall ever having ran anything more than a two miler to the swimming pool. You should not be failing once, let alone twice.
This may sound harsh but have a serious think about whether this is the career for you. 3 commando brigade exists to do things that others physically, or mentally can't. There are enough Friday night marines kicking about the corps as it is, what we need is highly motivated, physically capable and switched on grey men. You've got the motivation, or else you would have disappeared into the shadows by now, what you need now is the physically capable part. Do not rush your final chance.