In theory, yes. Several of the channels that publish on PeerTube and YouTube have referral links, sponsored segments and the likes - The Linux Experiment and Gardyner Bryant are two big ones off the top of my head, as you also pointed out. There's a support button integrated to link to Patroen/Liberapay/Ko-Fi and the likes, and during their AMA over at !opensource@lemmy.ml three months back, they mentioned having better Patreon integration on their radar at least, although not a huge priority at this point.

In practice - it comes down to the chicken and egg problem again, as well as currently a lack of discoverability. One reason creators put up with the BS on YouTube is that, even when ad monetization is basically nothing worthwhile at all for the vast majority, and the algorithm also forces them to hamstring their creative process at times, it is the one place where people are most likely to discover your videos, thanks to the algorithm being trained to keep the audience engaged in addictive binge-watching, and the way it - to its credit - can also sometimes push small, still unknown creatives into people's feeds if the audience could be interested in the topics/video style.

Now, an addictive, obscured algorithm like that would rightfully be anathema to the principles behind PeerTube, but there have been some attempts to create better discoverability. This Firefox add-on is super basic, and it doesn't seem to work without hiccups - but it did help me discover some stuff at least. Communities like this one here help with word-of-mouth discovery. And some creatives that are focused on the Fediverse leverage Mastodon integration to engage with their existing community there, and have those users as their main audience, which can quite seemlessly interact with videos through mastodon.

So, in theory, there is nothing that would prevent living on PeerTube alone, ad revenue from video ads is not nothing, but for many, it is not the main source of income, sometimes basically just pennies. Referral links and sponsored segments work just the same as on YT, basically. In practice, the community is still too small, so most creatives will opt for publishing on PT and YT simultaneously, if at all - very understandably so, with varying levels of taking PeerTube seriously and putting some effort (like engaging with comments on there, or checking if your YT-imports actually succeed and such). Increasing that number could help with growing an engaged community on PT, which would then increase the attractiveness of it - potentially to the point where one day, it could become more feasible (alongside other potential developments, like better integration of PT with platforms like Patreon/Liberapay/Ko-Fi).

Not via peer tube directly ATM. There's no real monetization etc built in a far as I know still. You could combine it with something like patreon and then yes. Absolutely in theory.

Someone big like gamers nexus might be able to roll support and audience over. Might. But it's not as simple as that either. They would likely end up rolling their own service. Which could bring it's own new legal headaches. They should still explore it. But it isn't a panacea.

Some instances have profit sharing with their creators. Its a novel way, but probably the best bet is to use something like Patreon or the "Support" button on the peertube channel themselves in order to support the creator.

Also there is nothing stopping instances adding ads to their main site...if they wanted to. Most do not for obvious reasons.

No. Not at this time.