Just put a change object going to a "sel 1" object. The left outlet of sel will give you a single bang when you press the key, the right outlet of sel will give you a bang when you release the key.
Put this in place of your change --> counter thing you've got in the "tab_5" subpatcher. The counter object you've got there is pretty pointless, it's just outputting the exact same thing that the change object is outputting.
Your patch wasn't producing a huge amount of bangs when I opened it, just two — one when you press the key and one when you release the key. The foot_on data coming from the SoftStep seems to be outputting a huge amount of 1s and 0s — a change object (like you already have there) will kill that.
2, 3, 5, 13, 89, 233, 1597, 28657, 514229, 433494437, 2971215073