There is also 3:3 - וירדתי.
There is also the vocalization in the Leningrad Codex of 2:9, והלכתי
(the first one).
I don't think the 2:9 is really relevant, but it is still interesting.
As for 4:5, I don't think it is related but it could be explained as
originally standing
for "I bought off my duty to redeem the name of the dead." Perhaps it
is just the
result of the fact that all other times he says קניתי.
Regarding the idea of a Freudian slip, I don't think it really
elucidates the text. Are
the examples in Ezekiel or Jeremiah Freudian slips? However, there are modern
languages where the feminine differs from first person. So we can actually
test
the idea of these "Freudian slips" by seeing how often it happens there.