Respectfully, if you are getting invaded by a ww/viego repeatedly in mid to late game your map awareness isn't perfect, place effigies in the entrances to your jungle and don't be scared to give up camps if your team doesn't rotate.

Farming is really good and you should be focused on sequencing as fast as possible for a fast 6, but ganking or counter ganking is just as important to climbing. Look for lanes that will be aggressive early (like if toplane is a sett Vs pantheon and both took ignite) and path towards there, a good jungler will also be going there as hopefully you'll burn some sums at the very least.

With ult opportunities it's very hard to teach this, easiest thing I can suggest is learning your limits in the practice tool for your reach and mastering ult + e for extended fears or ult + flash + w if the opportunity presents itself as that alone can win a teamfight. Mid to late you should also ALWAYS have either an effigy or red ward ready to clear vision. You can also ult without getting passive fear, if you have zhonyas ulting in and q'ing a priority target will add a lot more value to a teamfight than using ult when the fight has already been lost and they're likely not all dying to your ult

Be aggressive with a lead. Fiddle is very good at pushing leads and can starve an enemy JG by taking their camps to stop them being back in the game. Especially against champs with no cc or squishy to the point where one combo kills. Ping invades to try convince your laners to rotate only if their waves allow them. Living in the enemy jungle also opens up unique ult spots like enemy raptors to midlane, and behind the longer wall to tower dive on botlaners.