2) Not all foundations-behind-open-source-projects use revenues from hosting as their sole source of funding. Notable examples include the Blender Foundation and the Linux Foundation.
For #1, that is the kind of logic that works fine for the early adopters, but frustrates and turns away the people who just want e.g. a Substack that won't squeeze them for login walls or a Wordpress that is easier to use. I've seen a lot of non-technical people in that bucket turned away recently by Ghost (Pro)'s opaque and confusing member-based hosting costs. It makes it completely impractical to run a free email newsletter, and plenty of other Ghost providers seem to have this worked out. So all it takes is one of those competitors breaking through to achieve name recognition and get a lucky roll of the marketing dice to overtake Ghost in revenue. And then they can fund their own fork and the Ghost community is forced to agree to their development wishes or become outpaced by their proprietary features. It's a pretty bad place to be in.
Or the number of customers who would pay an $X premium to have "Ghost(Pro)" over another host (at the same features) will be roughly equal to the number of people who would spontaneously donate $X anyway. We have ample evidence that affection isn't enough to keep FOSS financed unless the developers are very visible and the ratio of developers to users is very low.