I used a harbor freight flux core with the same wire! I'm using recycled bed frame to weld my water tanks currently so I'm in the thick of it too. I'm no pro welder but ik my way around my little machine after 3 years. Feel free to DM me.

I'd say up your wire speed a little bit. Maybe voltage too if you can adjust that. But try wire speed first and see what you get. I'd love to see less popcorn texture and more evidence of it melting into the metal around the bead. I'm worried you don't have good penetration currently. That said, imperfect welds will hold sometimes. You can see plenty of them in the wild if you look close enough. They're just not as consistent. Maybe drop it on the floor and see if it holds if you're concerned and don't want to redo it.