So I just got my F and F#m barre chords to ring out nicely recently. I tried going up the neck towards the bridge using some different shapes. But as I went closer towards the bridge (around 10th fret) I found it much more difficult to rotate my index finger. On the lower frets I could rotate my index finger so that the more bony side contact the strings. But higher up on the neck, I found it almost impossible to rotate my index that way due to my left arm approaching the neck in a 90 degree angle. What am I doing wrong and how can I fix it?
In my own instance, I find it unnecessary to barre chord clear up to the top of the neck for a couple of reasons. One reason is the angle of my arm as you have mentioned, but even more problematic for me is the closeness of the frets that high up the neck. There are some movable chord shapes that do not utilize the barre finger. Perhaps they could solve the problem when you can not rotate your first finger as you prefer to do, still allowing you to use those higher pitched chords. Another technique I have used when I'm forced to play up that high is to push the guitar forward (in the direction of the tuners) which will temporarily change the angle of my arm to the neck, more in line with when I'm playing further down the neck. For the most part the only playing I do that high up the neck is licks and riffs, not chording.
You could try to hold the guitar to the left side instead moving with your arm across your body.
It is not forbidden to practice the barre chord (234 borrowed from E major) till the end of the neck, as long you don't suffer. But the next step you will learn is the barre chord based on the pattern of A major and you will be able to transpose and reach the same chords quite easily.