As far as the resolution: It has to do with the fisheye lens. its not as sharp as a "normal" camera due to the pixels per inch being much less due to the wider area of coverage the fisheye lens offers. I can see where a narrower lens would be optimal in some scenarios but I think there would be more scenarios where a fisheye lens would be more optimal for this type of camera.
As I said above consider a Mobius C2 lens if you can make it fit . The HFOV is reported as 132 degrees for the Mobius lens, and should be more than enough for a decent view. I wouldn't describe it as optically perfect, but it's a good lens and in use in a lot of situations where wide angle is needed eg. It's widely deployed on RC Aircraft, as a Dashcam and in other uses. At $10.95 retail, the trade price for the lens is unlikely to be high, and it's coated glass not acryllic.
It's worth remembering a wider field of view isn't better if it's distorted. The aim of a doorbell cam isn't to see someone coming to the door, it's to record them and to that end it fails if they aren't easily recognisable.
I'd also say you have very little to lose by testing a Mobius C2 (beware there are other lenses - A, B, C (1) and D (some now discontinued))or other glass lower distortion lenses to see if you can improve the picture further.
However, nice product so far. Just would like to see a bit more image quality.
This is an image from a B Lens, (replaced by the C2). The B lens is only 116 HFOV, but as you can see, it still manages to capture most of the dashboard when mounted by the rear view mirror. The image quality is also quite good, free from obvious barrel distortion and pretty sharp - I rendered the image actually quite low quality (50%) so it's sharper on the original and the C2 is sharper still:
Mobius B Lens Video Capture Screenshot:
Mobius B