Hello libbert.co,

1. Header: Fixed, please clear browser cache and check again https://prnt.sc/Yh58lPK603sn

2. Footer: Default style usually has top or bottom spacing to make content readable, for e.g: white spacing above footer caused bottom value of main content https://prnt.sc/Z7X2muVs9GnD and tabs bottom value https://prnt.sc/yj9fieqBYAoz

If you want to remove it completely, please use below CSS:

.single-product .product-tabs-wrapper{
	padding-bottom: 0;
}

.single-product .poduct-tabs-inner>div:not(:last-child),
.main-page-wrapper .site-content{
	margin-bottom: 0;
}

3. White spacing after footer: Because you turned on Sticky add to cart option.

Regards,