Yes, it got removed Now there is a way to obtain points/gems other than buying that is by filling survey, but IMO it's quite complicated
Yes, some selling gems (or "can be called" GP before) or buying items like reskill, restat, puke, etc then selling it on game.
So far cheats and hacks are hard to find now Except scammers. Be careful of those jerks.
Yes, except you can't enter Date Dungeon alone ofc but there are always people who search for DD partner. Most people using 2 clients for faster leveling at DD (but that kind of thing is somehow a bit lonely ). Also, exploring the land by yourself is ok too (since the EXP rate is high).
All I know those job you stated above are good for war
That's all I can answer . I'm still inexperienced so please correct me if i mistaken something