blurry pics, left alignment, and pages not in agreement

I’m trying to update/improve a website but I am running into problems and no about of forum searching has been able to reliably help. I have managed to fix lots of things partly, but nothing is consistent.

Here is a link to one product page of the site: https://fullscalefx.com/product/pool-heater/

This page is perfect except for the add to cart button/quantity counter. We do not want the add to cart button on any page of the website.

Here is a link to another product page: https://fullscalefx.com/product/spray-snow-in-a-can/

The add to cart button is gone, but the page is squished to the left, and the related images are too big and blurry.

Originally, the layout was consistent throughout the site, but the add to cart button was present on every page and all the pictures were blurry. Every time I try to fix something it only works half way and messes up other things.

I’d love any and all help you could give me. I am a beginner and am just trying to figure this stuff out as I go. Thanks!