2: They store the same number of values as unsigned, it's just handling of those values and comparison operations differ. A signed and unsigned 32bit integers store 2^32 values.
3: Crypto algorithms do not operate numerically, thus 2147483647 * 100 will yield exactly the same result for uint32 and int32 as much as any crypto algorithm is concerned.
4: Therefore you send 2147483648 in binary form as 4 bytes = 0x80000000
As a server-side tool it has been getting taken over by Ruby/Rails, Python and the stuff mentioned in the OP.
I hope you are kidding here, because that is far from the case. Java is still the de-facto language for most server-side applications. RoR never outgrew it's hipster background. It has been 7 years since RoR had it's hype peak... The hype waned and RoR is still a rarity.
Java developers tend not to have issues with future proofing for new functions in interfaces.
Consider that you are targeting a DnD players in Boulder(CO), going through Google is the least efficient tools that you could use to get personal details about your target group.
Targeting any group larger than that is pretty much useless and you can't practically gather any valuable personal information.
Please note, that private information is only the information that can personally identify you. Unless you happen to live in a country/city that has you are the only person fitting that profile, you have no basis to claim that your private information is sold.