I'd like to correct a few things. Feat-wise Tsunade has more chakra than Gaara. If you consider the fact that not only did she heal the village twice on one occasion, but she healed 3 kages (Gaara included) and replenished their chakras, healed from 3 Susanoo Swords, 3 Yasaka Magatamas, Madara's massive katon that was meant to attack all five, attack Madara, and take on 5 Susanoo clones before she needed a heal.
First of all,tsunade managed those feats because of her yin seal,which contains chakra she has stored over the years,her SOH forces the chakra out much faster than rebirth,which means she will heal faster,but when the chakra was depleted,she was weakened.she healed gaara and onoki only,and that isnt much of a chakra feat,sakura healed might guy from the 7th gate,does that mean she has more chakra than him?,sakura healed naruto's injury from the 4 tails,does that mean she has more chakra than him?. she healed the village once,that was before pain then destroyed it and she was out of chakra after that i think,also how many shinobi had died already and how many did she actually get to anyway?. Gaara had been using his sand in the air to fight deidara,used several high level techs,was able to block a nuclear bomb with his sand,after deidara detonated those bombs,he was still able to move the entire sand above the village towards the dessert. In the war,he has been been fighting for 2 days straight,using top class techs,helped stop a meteor,then tanked another one,blocked massive explosuons,and having his SAND ARMOUR on at the same time which is very chakra taxing,he also helped block madara's magatama. Also,gaara had also been fighting those susanoo clones as well,and didnt run out of chakra as well. His former jin status and the fact that his 2nd databook chakra stats have him above tsunade's 3rd databook stats is clear that he is well above her in chakra.
While Muu may be more experienced he did not have a way to stop Joki boy given his abilities. Had he used Gold then sure, but Gaara was lucky enough to have his father brought back. In addition, Tsunade has shown pretty great intelligence feats in addition to strategy.
Muu had a lifetime to figure out the weakness of joki boy,it's not just that his fighting style isnt suited,he had no idea how to deal with it at all,he had earth wind and fire techs,you think if he knew it's weakness he wouldnt have thought of something?,gold isnt the only thing that absorbs heat or can be used to counter jokey boy,gaara can't even manpulate gold,he hid it in his clone,don't you think muu would have done something like that of he knew it's weakness?. Also getting minerals like gold and such from the ground is easy for gaara,his shield of shukaku proved it,he selects the hardest minerals fot the tech,he can use his sand to bring out gold as well.
Acid and Fire are very separate things. Acid doesn't burn because of heat. When Katsuyu's acid burnt through the rock, Amaterasu didn't burn through any of the Uchiha hideout. Considering Katsuyu's acid was able to burn through solid stone it should be able to get through Sand. You also failed to take into account that Katsuyu is impervious to squishing, slicing, stabbing and other forms of cutting or crushing. And She can divide at will. Gaara honestly has nothing in his arsenal to deal with her.
