though I understand it's the max rating and it might require some extra cooling)
No it is actually imposable to run this chip with all the outputs switching their maximum simultaneously.
See:-
http://www.thebox.myzen.co.uk/Tutorial/Power.html
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html
For true isolation you need an opto isolator something which DC SSRs have built in.