1. Q your ball out
2. Get into melee range to bait a fight
3. E+W your ball back in
4. Autoattack to death

Maxing E first will give you unexpected sustain. Your passive + item on-hit effects + thunderlord's will end the fight very quickly.

You are dealing both physical and magic damage with each auto, making it difficult for tanks to counter.

For full burst when you have Guinsoo's Rageblade, start AAing minions as you approach the enemy champion. If you get to 6 stacks before the engage, game over. Most players expect Guinsoo's to kick in much later because this trick is difficult for the typical melee wielder to exploit effectively.

Absolutely.

You can take this exact build to the jungle, except grab a Hunter's Machete on first buy to get you your XP. You can ditch the Machete later, or build it into Bloodrazor. However, Bloodrazor is not as good as Blade of the Ruined King, so you'll want to swap it out when you have the gold.