Get that item on your support and ADC. The ADC won't fall too far behind from 365g early and then 800g mid game.
Both, your support and ADC will have a lot of sustain due to the execute, the HP reg and max HP.
In a 20 minute game you can make around 800-1k gold with it, making both items more than free after this time and you still got 175 HP and 12 HP reg + execute (easy farming).
You will be stronger as long as you don't fight long 2v2 fights in the bot lane (you are winning short trades with the double sustain) and even if you lose, you will still make way more gold than the enemy.
1. It gives gold equal to the kill + x is not a good idea. You now want the support to take the canon minion or a melee minion to max the gold output. Change it and give the support a fixed amount (e.g. 24/35g) while the ally gets the kill gold (and maybe still a small bonus).
2. If you take a CS without the execute skill, the CD of the item will be stopped for 5 seconds.
And pls show the CD in the item (I'm pretty sure you are already going to do that).
The current item can give you around 600g in less than 18 minutes. The other items give you around 300 (philo) and 400-500 (Kage's) while Kages also needs way more attention to get enough gold out of it.
Both Philo and Emblem build don't need any real skill to use. Philo has a short downtime when you are not in lane. Emblem doesn't have that problem cause you have 1 (later 2) minutes till you have the full stacks and then you can unload all of them in one wave.
For me the emblem build was already the strongest before this patch, but now that you have even more time to use the stacks, it got even better.
I think all 3 support build paths should have a ammunition system where they can get these stacks over time and unload them all in a short window if needed.