Me vs My Mom

I have a wife of 9 years

N my mom has a sorry bf(doesn't work and lives off of her but that's neither here nor there) of 8 years

Me and my wife have a beautiful son named Mason Mccoy

So 5 months ago during a family outing my moms bf(Shawn) decided to bring up How my son was conceived

Me n my wife used a know donor whom we now Co-Parent and he ejaculated and we used the stork to do a home insemination

The Male figure is referred to as his dad

This figure has not contributed to the well being of our son who is now a year old

He hasn't brought anything or giving any funds to help with Mason

So shawn became intoxicated and started to speak all his thoughts 2 of those thoughts were

"I know yall had sex with him he dont look like the type that will nut in a cup"

This pissed me off but I kind let it ride but the second comment turned me from 0 to 1000

Shawn then proceeded to say "Yall keeping Mason from his dad just because yall making money this boy needs his dad what if the man was making the money and he kept mason away from yall how would you feel"

I proceeded to say" I took my son down there for 3 months to see this man even though I knew he wasn't helping out I gave him time to help out Im not keeping Mason away from him if he help out he can defiently see mason we dont need this man's help we both making 40k a year but he agreed to have a child but he doesn't wanna help take care of it"

We asked the Co-parent to sign his rights away he refused but doesn't wanna help

While he was talking he slipped up n said Me n the Male was the parents totally excluded my wife

So I took my wife and my son n my son's stuff and I left

I let my mom still see him n come by and my talks/video chat every day and she knows how I feel about her bf n she says she respects that

So now 5 months later I got a new job and I let my mom keep my son because daycare said by him being sick he couldn't come back until he felt better and she promised me My son was not around her bf for the 8 hours she keep him and today I videochatted her on break and realized my son is near this man and mom lied to me

I wanna drive over there knock on the door grab my child and his stuff kiss my mom n leave but I know that will cause a problem but im tired of people not respecting my marriage or our family

How should I handle this?