Your info very confusing (at least to me).
In post 22 you show a signal on your scope , is this signal a Input to the Nano or a Output from the Nano.
On the Scope in post 22 the Vpp is 449mV , for a Input its to low , for a Output its also to low.
Did you manage to read a known signal on the scope , like Blink in the examples but just way faster?