Thank you for your reply!

I am attempting to play the B7 as described in the Quick Change Blues guitar lesson.

The reason why I got to that position is that if my thumb is not that high I cannot mute the A string with the thumb, if the palm is not so close I don't have much strength in the other fingers nor precision with the middle finger. My thumb doesn't seem to be able to bend much over 60 degrees (not sure if it is healthy to stretch the articulation to bend more).

If I try to mute the A string with the index finger, I don't seem to be able to have the high E play nicely. I also feel a lot of pressure on the side of the thumb that touches the neck

I will let my hands rest for a day or two, then re-read very carefully your suggestions and then play around with it again trying to relax as much as possible.

Hopefully, the rest of the Blues course is not based on these chords or I am screwed Ahah.