Very nice. This is a good song and well worth the extra effort to do something with the middle.
Since this is still a work in progress and there is some discussion regarding the overall length of the song, I suggest the middle where you're placing the solo can be substantially shortened without harming the essence of your song. After several listens and focusing on that section, I don't see where a solo is going to add very much to the overall build of the song. You could easily shorten it to a two bar section and find a solo phrase of that length.
It may be your issue all along in finding a suitable soloist is that the song is telling you it is unnecessary.
I hope you share your final version with us here on the forum. I enjoyed my listen a lot.
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