I will comment first about your last night, for Lisbon, the airport is almost within the city, maybe a 10-20 minute ride from central Lisbon, taxis are cheap, Uber cheaper, seriously we paid like 10 to 15 euro. So no need to go out of your way to stay by the airport, stay in central Lisbon.
Aside from that, for food, we randomly hit a few places right in the heart of Lisbon with pleasant results. I wish I could remember exact names, but in our wanderings we looked at menus and the place, noting it for trying later. One happened to have a number of specials, including a Lamprey dish, tried it, it was good, not sure though I would go out of my way to get it again, but worth the experience.
They have several markets worth a look; the Mercado da Rabeira is near central Lisbon with half of it taken up by the Time Out Market, a big food hall with stalls serving all kinds styles and types of food and drink. Several top chefs from Portugal maintain outposts there, so you can find some neat dishes.
Maybe the famous (infamous?) recommendation for foodies is Ramiro, a seafood place. Anthony Bourdain ate there, as well as a couple other TV chefs, we looked at going there, but with the crowds and lines it seemed more trouble than we wanted. Reports seem to be up and down whether they have suffered in quality and service since their "discovery", maybe with the pandemic things have settled down. I am always leery of great restaurants that get hit with a deluge of fan-boy customers after a TV show, seems they become an expensive "meh" experience. There are other similar seafood places, that might be worth a look.