You’re asking the camera a lot with those usecases. I’m not sure but in this post there may be something that could help with piping the image more directly: Lib[rem5|camera] to use everywhere - #8 by galilley but the noise ratio of the camera may be a bit much for stars (depending on the quality you want and environmental factors). Astrophotography forums may have better answers.
With sun, prolonged exposure is a risk. I’d get a sun filter and tape it (or do a 3D printed holder that you can slide) into place when taking a sun picture. You’re unlikely to get any details of it without one and even still, with wide angle lens, it’s probably just a small bright dot. Again, astophotography forums and sites have better info available.