For me its a good read material. Concerning “boob” brained, most of many other novel male MC is also “boob” brained. So its not really a problem. Maybe just some way to ease the tension.
1) The writing? I don’t really understand since Im not a literature guy, and most novel I read because I like the story and characters. Even some bad grammar did not really bother me.
2) Yup, its considered spoiler, but if you dont mind spoiler; I think Rollo is his divine beast companion that give him purpose on his journey. I mean, his journey basically has become “how to make Rollo get the full powered form again”. Forewarning, my spoiler may not really accurate and only personal rambling of one of the reader. Lol
But all those aside, I suggest you to try to read it at least until he meet the female character on the first vol cover.

The parts I translated so far has not much boob brain stuff. At the very least it is at the same level as many other Japanese novels, though he gets the deed done unlike many other Japanese novel MC’s
1.) That’s something subjective. Everyone likes different styles after all.
2.) That would be a spoiler if you are reading from the start, I think. 🙂

Is this a good read material?
I mean, there has been some hateful bash about MC who is ‘boob’ brained.
1) Is the writing itself interesting?
2) Who is Rollo? companion? summoned beast? slave?