My boyfriend fools around too much = This is a habit, he does it all the time.
My boyfriend is fooling around too much = This is something he is doing right now, at the present time. It doesn't necessarily mean it's a habit.
Out of curiosity, can I check that you know that "to fool around" can mean "to mess about/have fun/do silly things" but also "to cheat on your partner"?
The addition of "always" would make the use of present continuous acceptable. But I wouldn't consider "always eating ice cream" an example of fooling around. Wasting time instead of studying, working etc. would fit better with the term.
Out of curiosity, can I check that you know that "to fool around" can mean "to mess about/have fun/do silly things" but also "to cheat on your partner"?
Or not necessarily 'cheat'. I was confused when I first met this in a film, when Frank Sinatra said to his date 'We could always just stay home and fool around. It was then that I realized that'fooling around' in Am E means roughly the same as the Br E slap and tickle' !;-)