Overview
Instead of listing every single small pro of Chesnaught, try to merge them into pros that describe Chesnaught's effectiveness in the metagame:
- Decent physical wall that checks some dangerous offensive threats (Aegislash, Excadrill, Tyranitar, Garchomp)
- Decent annoyer with Spiky Shield + Leech Seed, which is particularly effective against VoltTurn teams
- Has reliable recovery and decent offensive presence
As for its cons, its big list of weaknesses, inability to check many dangerous physical attackers, and low Speed are its main ones. Its HP is decent and its movepool is big enough to do what it needs, so remove those two.
Main Set
Moves
Hammer Arm is a solid STAB option that can deal damage alongside Leech Seed.
Hammer Arm is useful to immediately deal with threats weak to it, such as Excadrill, Tyranitar, and Ferrothorn, not because it has any particular synergy with Leech Seed, so be sure to change your sentence.
Synthesis is useful with outlasting Mega Venusaur and keeping itself healthy when the damage from attackers is too much to heal from Leftovers and Leech Seed.
Synthesis is useful to have any kind of reliable recovery when Mega Venusaur is on the opposing team, not to fight it 1 v 1 and pp stall it. It is also useful when you are taking big amount of damage, where Leech Seed recovery just isn't enough. Change your sentence accordingly.
Roar is a useful option when a sweeper sets up and they won't switch out from Leech Seed for obvious reasons. It can also disrupt momentum from switches from Leech Seed.
Provide some important examples (SD Aegislash, Sludge Wave-less Gengar, SD Garcomp).
Usage Tips
Remember that Chesnaught has Bulletproof! It gives it a wide variety of switch in options such as Aegislash and mixed Mega Lucario.
Mixed Lucario is very rare, so replace it with a better example, such as Gengar sets without Sludge Wave.
Explain that Leech Seed should be spammed whenever possible (when the opponent lacks Grass-types), and that it should be followed by Spiky Shield if the opponent doesn't have set up moves.
Team Options
Barbaracle hits Flying-types with Stone Edge and is capable of using Chesnaught's chip damage to get past walls it normally couldn't.
Replace this with a more relative example.
Other Options
Remove everything you have there, those are all useless options. Instead, put Spikes, Stone Edge, and Seed Bomb.
You are also lacking a ''Set Details'' section, so make sure to include one.