First of all, why do you want a Poison Type Pokemon? Doesn't that overlaps with your Venusaur, and also why not Nidoking?
It's found really early in the game as a Nidoran♂ and then after evolving it into a Nidorino you can use the Moon
Stone to evolve it into a Nidoking and it also really helped me against Lt. Surge but you have a Venusaur so I think you have already defeated Lt. Surge.
Ok back to the question, so obviously Muk is better than Weezing. It having a base stat total of 500 and having more Attack, HP and Special Defense to tank most of the hits. However, iff you want to have good Defense then Weezing is having a really good Defense stat of 120. But I still think instead of having a Poison Type Pokemon you should have a Ground or a Fire Type Pokemon. Or, you could Just use Nidoking and you should.
And you should probably replace Primeape with the Hitmons [Hitmonlee And Hitmonchan].
I hope this helps!