If you are willing to use a long enough keyword, you can decode any text into any other text!

So my BS meter was going off until this point, but actually, 45 letters isn't a really unreasonably long keyphrase at all. Eight words is a compromise between single-word keys, which are fairly easily broken, and a one-time pad, where the key is longer than any possible message.

If you use a 45-letter keyword and you get intelligible text out of the code significantly past the first 60-ish characters, then it is a near-certainty that you have the right key.