It "Consumes a stack" of Manamune. Sorry if I made a typo somewhere but should still consume a stack from the Manamune item

It is possible and I have never seen this happen. This guide goes from items/Runes from the top Ezreal players on the Korean ladder. I could try it someday and come back with feedback. If you have any other pro/high level player doing this feel free to share it to me and I'll look more into it.

It also plays a role which matchup you are vs and the lane state, but overall I think using a whole TP just to get a 400 item is a bit too much. But I am open for ideas :p

Riot is looking to buff all of the ADC items, this is pre-season so the build changes weekly. Atm I would say go Divine but this could change if Trinity gets a buff or Divine gets a nerf, which is likely to happen.

One item each "Spellblade unique passive" :p

Hey, thank you, I am glad you liked it :p I recommend going Conqueror but if you really dislike the rune and want to try something else, going Arcane comet or even Electrocute because you gain some life steal runes there. However, the problem with these runes are that you are going to miss out "DPS" (Damage Per Second) You main role as an ADC is to deal dmg over a long period of time, and Electrocute and the Domination tree does not offer this. Lethal Tempo is also a choice but it is hard to play with if you are lower rank or new to Ezreal. You will be going Blade of the Ruined King later on to make up for some of the lack of healing