How do you practice to prepare for your performances? It sounds to me like maybe the parts you’re trying to play you don’t have quite as much command over as you think you might. I don’t mean any offense by this, but performing on stage and practicing at home are two totally different animals. One of which you have control over the environment and the other you have minimal to no control. So if your technique needs a degree of environmental factors to be in place that you’re unable to achieve when playing live, yeah you can experience greater tension and less control live. Anyone who’s been a guitar teacher long enough to have experienced a student coming in saying “but I played it better at home!” knows what I’m talking about.
Do you practice sitting down or standing up? Do you need to be warmed up for an hour or can you run your set after only 5-10 minutes? Are you playing through a similar tone or close to it? Do you pause and go back to fix mistakes when you run your live set or do you try to correct on the fly?
There are a lot of good articles on the www.bulletproofmusician.com blog that talk about practicing for performance and how that looks different than practicing to improve technique etc.
I’m mentioning this because I’ve played so many shows in so many different degrees of being able to hear myself and that has never been a factor in how my hands perform, but preparing the right way at home does. And personally I’d rather change my approach to practicing for performance and see if that helps before dropping over a thousand dollars on new gear to try to fix it.