I am glad you are being so honest in a public forum. I am in my mid 40s, married my high school sweetheart but even prior to us knowing each other, I share many of Ichikawa's experiences at around age 17. And for those that I don't share, they seem completely plausible it's just not possible for one person to touch so many bases in 1 year in real life.
What I find odd is the choice of age for the characters. Is it really possible at age 14 to have such depth in emotion? In your uni days you would have been at least 8 years older than Ichikawa no?
When I got my girlfriend was around me having 20 or so years old. Playing devils advocate, yes, it is possible that Ichikawa would hold such feelings, but this requires an immense amount of solitude (in fact, I think the author got this right, as I was quite alone back then and my mind wandered a lot... just not reading whatever Ichikawa is reading).
However, What it is not so feasible is Ichikawa totally suppressing his hormones for so long, I mean, seriously, in adolescense hormones and emotions are out of control and we would not be adults if we weren't able to control them.
For both Yamada and Ichikawa, given the amount of affection they have, passionate encounters would already have happened and from this comes several important decisions, because time is inevitably running and both of them are slowly but surely turning into adults.
Decisions need to be made and here is were I see the author is loosing it a bit, as she does not understand very well the mentality of Ichikawa. Because she does not fully understand him she is simping him and this is totally wrong.
As a man who holds passionate feelings for a woman he would at least talk with her what exactly she wants for the future, as a plan needs to be made in order for them to be together. If a silly answer like "I do not know, we will see in due time" is given, no plan can be made and this also would seriously hurt their relationship, as nothing can be taken seriously by leaving such important step into the hands of luck.
We know however that Ichikawa does not like luck, therefore I would think that if the relationship is at a stake he would put serious effort into making a plan for both of them to be together, but again, they really would need to talk about that, if they really want each other for the rest of their lives...
but to be honest, this is a bit beyond of what an adolescent guy and girl can even manage to foresee, then again this is a manga, if anything, the author can make both Yamada and Ichikawa quite enduring for their love, and just perhaps... allow Ichikawa to be in the frame, leading the relationship somehow into a path that both of them can
be. The author has made until chapter 111 Ichikawa somehow the one that leads the relationship, and Yamada likes to tease him a bit in order for his feelings towards her to arise.
One can just imagine.