I haven't looked at your videos and I am not experienced enough to comment on stride length however I do have two observations/comments.
1) The muscles trying to keep your lower leg, knee and ankle aligned as your foot lands and pronates lack sufficient strength, hence the shin splints.
2) Shipo's initial comment about to much too fast is probably the reason you are having issues (the same thing happened to me a few years ago when I started running more). Back off, slow down whatever it takes to slowly build the base for more running.
(for the record, I am 6'3", 210, in my 69th year and training for my first half marathon)