Translation:I do not like him because he is not nice.
So, here's the impression I'm getting, please correct me if I'm wrong (I probably am)! I was so intensely confused on the varieties that I dug in and did some research.
"Dlatego, że" = "insomuch as", "is why that", "thusly, due to"; very formal. "He screamed thusly, due to fear", "He ate his sandwich, insomuch as he was hungry".
"ponieważ" = "due to", "because", "since"; more common for giving a reason, and in writing. "He screamed, due to fear", "He ate his sandwich, since he was hungry".
"Bo" = " 'cause", also used in several hard-to-translate phrases; more common for justifying a reason, common in speech, and less formal. EVERY use of "because" I've seen in the Vocative case uses it! "He screamed, because he was afraid", "He ate his sandwich, because he had hunger", "Stop, because I'll shoot!"
Your reasoning looks really well to me. Although I feel the three variants are closer together on the formality scale than the English equivalents, the literal translation are pretty much that.
Note, however, that you would use a noun after "due to" rather than a full sentence. In that respect the Polish equivalent would be more like „z powodu”. For example „wszystkie loty zostały odwołane z powodu silnych opadów śniegu”.
The first two sentences for me, although translated with different words to English, express basically the standard meaning of „bo”, even though you couldn't replace them with „ponieważ” or „dlatego, że”. The first one is also a casual expression where starting with „bo” is acceptable.
Personally, I would use „jako że” in place of „ponieważ” and add „postanowili” in that sentence.
It considers "ładny bo ładny" a different meaning of bo, but includes "bo powiem mamie" as the same meaning as standard.
If "Ponieważ" at the beginning is good enough for Iwaszkiewicz, Makuszyński, Polityka, and university textbooks it is good enough for me.
Also I personally consider "jako, że" very formal and a bit outdated