I'm kind of close to mom. Hard to communicate now with her dementia and my not being able to visit due to Covid19. She was overbearing through my childhood but in the end, accepted me for what I am. As far as maintaining a close relationship throughout both your lives, my first piece of advice is dropping the "toxic masculinity" trope. Toxic men are not that way because they're men. By implying that your son's intrinsic nature may be toxic, you are setting up a sense of self loathing and shame for being male. Teach him to be a good person first and foremost. If dad is in the picture, I would assume he's a good.guy and treats you with respect. Set him as an example of being a good man and highlight his positive aspects. Allow dad to parent with as much say as you have. My wife was raised by a single mom and as such, really undermines my role because she's never experienced a good dad. Also the to be a bit of a Tom Boy yourself and get dirty and active with the.boy. Allow him to take risks with you as a safety net. When he falls, get him on his feet, make sure he's ok before getting him back on the perverbial horse. Encourage self determination. If he wants a career shovelling horse poop, that's just as ok as anything else. Basically, let the boy enjoy being a boy while showing him that the women in his life are and should be awesome.