I agree that the problem is trying to use the metronome above your reading level.
Can try:
Slow it waaaaay down.
Break it up into the smallest component phrases.
Reading is distracting you from playing. Your eyes and ears are powerful senses. You are engaging both in powerful tasks here and coming out the worse. It's not that your ears are bad to know if your intonation is good. You're simply over saturated. You don't want to go fretted so that you're not dropping your fretless playing? Then drop the book and learn it by ear. Or go fretted and really focus on reading. Seriously. Baby steps man. Play this in the dark (that way you completely remove your eyes from the equation), no metronome, out of time, focussing on each note's pitch and tone. You will be amazed at what you can bring to it. Shutting off sight will allow you way more focus on hearing.
Play with a chord pad.
One great tool is cubase. You can sequence things and then break them down into components. Pick the smallest segment and repeat it. Then move on. Then enlarge the segments combining them into phrases and loop those.
Reminds me of when I was learning German. I got German books and their English translations and would read them together. First word for word. Then sentence for sentence. Got that sentence move on to the next. Finally go back and read the same paragraph to understand. Then go back and read the previous paragraph together with this one and so on. Meanwhile there's words I forgot the meaning of? Stop and look them up. Refocus on justbthat sentence to understand it, then the paragraph. Context of the word in the sentence. Context of the sentence in the paragraph. Took absolutely ages but I learned.
So you see, this is not "two issues". How many separate issues can you isolate here? Time, tone, technique, pitch, notes, shifting, reading notes, reading rhythm, playing by ear, attack, vibrato, finger selection on left hand, on right hand, being able to play without looking at your left hand, vibrato.....
All together it's overwhelming. Individually it's just an elephant to eat in small bites.
Jawohl!