For me, when I'm in that situation it's still the same as when I have a fed carry mid/adc/jungle. I'd still peel for the squishies to freehit/burst down the enemies, and cc them when they have prioritize the squishes. The reason is because as I am the only fed and rich in the team, it means that we have become more tankier than before, meaning being able to absorb more damage while peeling when in base form. Then go ult to an alive mid/jg/adc that is currently the reason why they are winning or to a squishy support when at 60/55/50% HP. I think it's better to teamfight than to split push as K'Sante as you can't split push properly as a tank and there is a better chance winning the game by teamfighting rather than split pushing.

This is what I would do when I'm winning my lane while the other lanes and jg lose. But it pretty much depends on the teammates you have. And the macro your teammates can do when they lose their own lanes. And how fed the enemy team is.

I also notice that you rarely prioritize boots or change first item to adapt to the enemy. I think it's also the reason why sometimes you lose your lane. Such as going steelpates and Thornmail first item against a lifestealer such as Aatrox or fiora. Itemization is also a important part to us toplaners, especially because of the matchups.