I think the sights mentioned are indeed all very nice and there's no doubt you should try proper hot pot - just don't wear your nicest clothes as they will be smelly afterwards. If you can't handle the spice, there's always the option of a split-pot where one half is spicy and the other non-spicy. Good compromise for us sweaty-noserunning westerners (and fear not, plenty of locals react similarly to the heat, they just really enjoy that )

If you don't mind the spice and if you like seafood, i would recommend the restaurant 蓉记香辣蟹爬爬虾. Don't know if there's an english name unfortunately, but it's spicy crab/shrimp-ish stuff which is indeed very spicy and very messy to eat, they even hand you plastic gloves (you have to get them out of the shell somehow..)! However, it's unbearably delicious and they also have non-spicy items which are also lovely (mainly garlicy-juicy oysters and similar things..).

Certainly a great experience and very very tasty - I go there whenever I'm in Chengdu. But you might need help from a local to find the right place. There are many similar restaurants in the same street.