To an extent: A character mentions having snuck into Keitaro's (the protagonist) cabin multiple times to read his journal when asked how he was able to rewrite the parts in it that he shouldn't have been able to know about.
During Yoichi's route, it's revealed that he was living on the streets for a long time as a child before being taken in by Yoshinori. Later, it's also revealed that before living on the streets, he was raised by his mother, who had abused him because he reminded her of his father.
Sort of:
In Yoichi's route, he ends up getting drunk during the party after the fundraising campaign. However, all characters in the game are 18+, and Yoichi in particular is 20 years old (which is the legal drinking age in Japan, where it can be presumed the game's setting is supposed to take place).
The Scoutmasters have been mentioned (and one seen) to have gotten drunk on a few occasions across the different routes, and in one instance they're reprimanded for not being good role models. However, nobody drinks enough for it to really be seen as any form of alcoholism.
No, although one route does revolve around that character's parent being hospitalized due to a "condition", although it is never actually said what their condition is.
Camp Buddy is an 18+ yaoi game. There is quite a bit of sex, and it is quite graphic. However, the story doesn't entirely revolve around the sex. There are sex-related minigames before each sex scene, though.
The game has multiple routes, each of which has a bad ending.
The ending depends on your affinity to that character towards the end of the game (usually by day 32).