As for the number of jumpers, I'd quess over 100 based on friends and family who were eye witnesses. There were people jumping or falling from number one even before number two was hit and both buildings stood burning for an hour or so after that.
I can tell you this, in 36 hours of working the line and digging inside the pit on the 12th and 13th neither I nor my oldest son who was with me saw anything left but ash...nothing (with one grisly exception) that was recognizable as human remains.
That day is definitely etched in all our minds.