Fahad,
Welcome to the crazy world of being a MUTT owner.
1st tell me, do you have an electric fuel pump ? Did you install it cause the ones on these are mechanical. Check that.
I doubt you'll get a newer tank, suggest you get this fixed, price is not bad as quoted.
A Suzuki carb is good on it, works well and very low maintenance. I have it on mine without any troubles, but I have an original Potohar one, not the chinese one.