how did Kuma know that Sanji have issues with himself and decided to sent him to Kamabakka and have therapy session with Ivankov
my respect for Kuma is just increased


Unironically that might have been tbe actual motivation. Lol. Kuma had limited interactions with the SH's (though he seemingly read up on them given he was name dropping all of them, and his mission to see Moria was connexted to them), but managed to mostly send them to places that would be helpful.
And he just coincidentally sends Sanji, the guy with serious self worth issues and a tendency to sacrifice himself for everyone around him (probably struvk a chord with Kuma, tbh) to the island run by the person who since the moment they MET had been lifting Kuma out of despair and making him fight to live? The guy whose legend is about being a miracle worker, who doesnt just solve everyone's problems for them, but instead helps people stand up and find a path to solve their problems themselves? Whether it was intentional or not at the time, it does retroactively make a lot of sense.