I think @Llyrel has covered everything in her comment and not much to add to that.
Your first decision must be what is it that you want? What are you looking to get out of this experience/ordeal (and yes, it will be an ordeal 100% guaranteed) that you are about to put yourself through? And you need to be 100% honest with yourself here and ignore all fancies of fortune and fame. Is this something you would do if you had neither fame nor fortune? The advice you mentioned was about getting more readers, so fame.
But there is something I'd like to add, something you might want to think about, and it actually links back to what Llyrel said in their comment.
You mentioned turning your fights into PG-13.
Is that your audience? Is the audience you want and plan to go after 13-year-olds and up?
If yes, then needing to change your fight scenes means you started wrong in the first place (I don't think that is the case though). It sounds like your intention was an older audience, so don't butcher your story and style to go after a different audience, that NEVER works. Just do you.
Do it the way you like it because you enjoying what you do is the only thing that will help you keep your sanity and continue on those difficult days. Again those days will come, it is unavoidable. Otherwise, I guarantee you won't last, and this is a LONG journey, not a sprint.
In my opinion, colour doesn't matter. Yes, it attracts more views originally, but if your work is good, it will attract people regardless and keep them, just maybe over a longer period of time. There are examples of successful B&W comics out there. Not having colour does not mean the comic is not good, and having colour does not automatically mean it is good.
Engaging in social media is actually way down the list for me. Where you should be engaging with is the platform you are posting your comic. That is where your readers are. It is extremely difficult to convince people through social media to come to a new platform to check out your comic. You have a better chance of targeting people already into comics and whatever platforms you chose to use. So don't expect that you will post on social media and get a lot of people.
So that covers 3 of the 4 advice you mentioned.
The last one is to make it vertical. This I actually agree with 100%.
If you don't do this, then this won't work as a digital comic. It can be a print comic that you edit for a vertical scroll, which means you intend on creating a print version some day, OR this is a digital comic first, so it has to be a vertical scroll design that you can then try to reform as a print comic if you want.
Truth is, whatever you choose as your focus, digital or print, the other version will not be that good and there is no way around that. Turning traditional comics into vertical digital comics will never be as good as comics created for digital vertical scroll specifically, and of course, the other way around is true as well.
Also, as you said, there is no whole page look in vertical scroll, but there are other scrolling techniques that will help you (if you go the digital route). So I suggest you try reading some of the top digital-only comics to get some ideas if that is what you will do.
I hope that helped.