A second opinion on your resume certainly couldn’t hurt. If money’s a concern, I think there’s a community on Reddit that allows you to submit your resume for review? Tread with caution, of course, but it could be worth a shot. Or I’ve seen people on LinkedIn or various job sites that help give back to their respective communities by providing resume feedback - I’d probably look for people in HR or who work as hiring managers.
That sucks about your business, but I think being honest about it is your best bet if/when it comes up. Businesses fail for a variety of reasons, plenty of which won’t necessarily reflect poorly on you. And if the gap is the last five years, well, there’s definitely been enough going on in that timeframe that you won’t be the only one with an employment gap.
I use a similar question: “What do you like best about working here?” I then follow up that conversation with a second question: “We all know every place has something they could improve on. If you could change one thing about working here, what would it be?”
I’ve gotten some very interesting answers to that second question. And because it’s not phrased as a complete negative - “what would you change” vs. the more common “what do you dislike” - it doesn’t put people on the defensive.