"She approached motherhood with the same bemused optimism she met everything else with," Oswalt tells PEOPLE in this week's issue. "She loved being a mother."
McNamara, founder of the website True Crime Diary, died in her sleep April 21 at age 46. Oswalt, who wed McNamara in 2005, says his wife "knew how hard" parenting was, but that she faced those challenges head on for Alice, 7.
"She was always honest about what frustrated her and exhausted her about it, as well as what her apprehensions were about raising a daughter, especially in this world," says Oswalt, 47. "She taught me it was okay to be honest and open about those seemingly negative things because, once you gave voice to them? They didn't seem too bad."
For more on how Patton Oswalt is honoring his wife Michelle McNamara, pick up this week's issue of PEOPLE, on newsstands Friday
One of the things Oswalt admired most about his wife were the creative ways she introduced Alice to a wider world.
"She made being a parent fun, which I'm struggling to continue through this shipwreck," he says. "Reading every night, and planning cool trips, and always scouring the Internet for out-of-the-way weekend activities around Los Angeles. And she has a sprawling legion of Irish siblings, cousins, nieces and nephews. Our daughter, through her, got very comfortable very quickly with meeting different people."
Oswalt admits he has a tendency to "get a little hermit-like" and that his wife helped encourage him to be around people more.
"She saw how opening up to other people and experiences I'd normally avoid made me calmer and stronger. But she was fighting back against 34 years of my bad habits," says Oswalt. "Alice had the benefit of learning from Michelle's example from the get-go. Now it's up to me to carry that on. I would be beyond happy if Alice were 80 percent Michelle and maybe 20 percent me. The 20 percent will probably be pop culture knowledge, but I'm doing what I can."
As for Alice, Oswalt says that she is honoring her mom in her own way.
"When your mom dies you're the best memory of her," Alice said, according to a tweet Oswalt shared Sunday. "Everything you do is a memory of her."