am i being dramatic about this situation?!?

ok. so last year my dad unexpectedly passed away. RIGHT after he passed away my moms guy 'friend' from work would come over to help with yard work and cleaning/taking care of the pool and basically anything my dad would usually do. so after like a month i started getting a weird feeling about something that was going on between my mom and this guy 'friend'.

one time i came home and he was freakin eating dinner with my family sitting in my dads chair at the table.

anther time he brought my mom over flowers but said it was just a 'friendly gesture'.

THEN one time i caught my mom and him kissing in the backyard! like a month after my dad died! WTF?! right (that was the last straw for me so now everyone knows i HATE this guy with a burning passion but the fam doesnt know all the details or anything).

so i confronted my mom, not about the kissing just about how its annoying that hes always over and she was like 'i ended it because he wanted to help around the house and then be paid in return with sexual favors, so u dont have to worry about anything between us, blah blah blah' AND this guy has a freakin parapalegic WIFE!

so every once in a while since then hes come over to 'help around'. he knows i hate him. i dont say hi to him or anything, i just ignore him. but he is scared of me for some reason, but i dont mind at all.

so my question is.... am i being dramatic about the situation for hating him? my mom is always like , be nice, dont be rude, theres nothing going on between us, blah blah blah

am i the one being immature and dramatic??? btw im 20 years old.