For me i don't see it that way. I ve seen parents do that to their kids if they misbehave or in this case refuse to eat and then scream for treats. I don't think it was to test the other guy, it was a form of discipline for his kid; u refuse to finish ur food, u don't get treats and don't throw a tantrum. The fact that he went to buy the ice cream was because he could trust the other guy to calm the kid down so he can behave. I don't think he intended to cause his kid distress. He seems like the kind of parent to put their kid first. Sorry about your experience, my mother is my greatest source of inspiration as well as a major player in my low self esteem. I struggle with loving her and fearing her at the same time.
The way the dad "tested" the MC really rubbed me the wrong way. I think it'll be okay for Ritsu since he did have someone there to tell him it wasn't his fault, but even if you've got a good reason, it's awful to cause a child legitimate distress like that. My mother is verbally abusive, and even though I'm in college now, I still suffer from anxiety and depression at least partially because of that abuse. So, the sort of thing that that dad did really doesn't sit well with me and prevents me from fully enjoying something that's otherwise a good story.