Jens did have 4 professional boxing matches and won all of them so I think he can weather Floyd's storm, but whe he clinches with Jens I think he gets tooken down and submitted by a Rear Naked Choke, and Floyd is not used to knees and he could get knocked out by some knees.
As for Hellboy, all I can say is dominance. He would take Floyed down and ground and pound him to death just like what happened to him against Ishida
, he can turn the tables on that one.
Let me know if you want me to go more in depth