Actors are people who exists outside of their work with their own hobbies and interests. Paul Rudd is getting paid to dress up and play Ant-Man only at his job, so he can dress up and play whomever he wants on his own time. (especially Weird Al)
Besides, if he actually dressed up as Ant-Man, everyone is just going to think he is a Paul Rudd impersonator anyways.
That and I doubt he wants to be shooting ready in an antman costume to walk around the neighborhood with his daughter.
His costume, other than the wig, is comfy as fuck. He can transition into whatever the night reasonably holds without have to have costumers remove the stuff and strip him of makeup, etc.
Besides, its probably in his contract to NOT portray his marvel character OUTSIDE of the movies, simply to retain proper branding. If he tried to put on his own antman getup, it would pale in comparison to a pound of makeup backed up by CGI artists.
I mean, I don't think anyone was expecting him to get fully decked out in his movie gear, if his daughter wanted him to be ant man I'm sure she'd love it if he put on a cheap Amazon "Insect Guy" costume. That actually would've been hilarious, and with a mask on he may not have even been recognized
You're using whom incorrectly. The first usage should be who. "Whom" is used when there is no associated verb. The second time, whomever, is correct because there is no verb that pairs with the word. "Whos" are subjects, and "whoms" are not.