Ok, I'll start with Iron Blood Village because that's what I know more about. If it's the first time you've reached the village then you can make your way to the main tent and do Orgram's Challenges. I'm assuming you're playing the public update, 0.37, so I won't say anything about the next update but that will have more content in regards to Iron Blood Village. You can also check out the animal tamer in the village and help him out with his stuff and that should give you access to roam around the village if you haven't already figured it out.
For Gunnar, I'll be honest... I haven't done his good heart route yet as I'm lazy and haven't developed my bottom route yet. Yeah getting a black heart is easy and you can reach -60 like if you repeat the action... let's see what that brings me in the future lmao. I know he has interactions in the Fair, where you can have more "fun". Also there is content if you finished the living aspect for Bernard, basically you make more houses in Bareshade and one of those houses will belong to Torben, the merchant that Gunnar works with. From there, depending on your relationship, you can do tasks for him I believe and that may be how you gain the heart. Hopefully this helps!
Edit: I also found he has moments in Northcrest in the public bath at the inn or roaming the streets (day) in Northcrest on Tuesday, Thursday, and Saturday. Just trying to find as many encounters as I can that may not be obvious.