Yes, you can play it.
Yes, you can play it.
Your i3 4170 with 8GB RAM and a GTX 960 2GB will likely deliver around 30 to 40 FPS depending on the game and settings.
You're looking for a processor with high IPC to match the demands of Arma III. You can consider DDR3 Z170 boards, and while Skylake might seem like a step back, it doesn't have to mean discarding your existing RAM. The i5-6600k offers strong performance, and its better IPC could be more beneficial than the 4790k's hyperthreading in this game.
I'm not familiar with either of these topics. The game does employ multithreading and it appears that even a 6-core setup boosts performance compared to a 4-core CPU, so I wouldn't want to lose frames just because of an i3. However, if the clock speed is very high, that could become more significant. Regarding Skylake, we might expect the improved IPC to help, but there aren't many solid benchmarks for Arma 3 that clearly demonstrate the issue, which means we lack thorough testing. I've been checking real multiplayer games that had problems, but I can't replicate mine. We can reasonably guess it would run better, though we're not certain.