Good Morning!
A couple of things, all this MT child support may be theory, because jurisdiction in WA, but it may also be leverage.
Please look up the WA child support worksheets and run the numbers there, then your son will know all the options.
Remember in the written materials from last weekend mom or GMA posing as mom, claimed baby didn't need a relationship with dad because she already had a spiritual father and a stepgrandfather, this statement will be seen as a parent unwilling or least likely to allow for the relationship with the other parent, this could be a strong factor in awarding custody and WA courts have given children to the father's before even when the child was well cared for. While not termed alienation, it is a form of aleniation.
Another factor, one admitted in mom's appeal is that she fled to MT because because she had no support in WA and it was meant to be a bridge tempoary, that is an admission that her curent residency in MT is not anticipated to be permenant and she could, based on her history of flight take off somewhere else, protected by another relative, remember her brother joind the USMC and eventually will be stationed somewhere far away from MT and mom could dissappear somewhere unknown to GMA and hidden by another sibling under GMA control. So this history of flight will factor into this as well.
These days a lot of emphasis is placed on the demonstrated behaviors of the parents and their willingness to co parent and to allow the child relaitonships with their other parent.
Insofar as bonding. Until a child is 2-3 they are very flexible in that regard. The better the visitaiton the better any potential transition. In this case, even if dad becomes cp, mom still has a place in WA to stay and have access to the baby. Let me give an expample. My grand daughter was born when both her parents were in the Army. They were both there as were numerous grandoarents, aunts and uncles. Mom breastfeed GD had to return to work at 5 weeks baby had some problems adjusting to formula but after a few different tries found one that worked. GD was held almost constantly. GD had a babysitter that was like a grandmother. Mom was deployed when GD was 6 months old, Dad became the primary caretaker, GD who was already a daddy's girl didn't really miss mom and was in constant communication with her with videos and telephone. Mom returned from deployment just after GD 1st bday then a few weeks alter, Daddy was deployed for 1 month, GD was inconsolable she couldn't sleep and was looking everywhere for her Daddy talking to Daddy on the phone didn't cut it, so for a week or so GD stayed overnight at the babysitters, who was a constant presence in GD life and mom had GD home after work and returned baby to sitters home until GD seemed more comfortable staying home without tears. a few weeks later Daddy returned and life went on. As GD was older there were other periods of time when Daddy was primary caretaker but not the same reactions.
Children are adaptive. In this case, dad is being given visitation separate and apart from mom so baby will bond uniquely with both of them. A part of that bonding will involve other forms of care such as feeding and bathing, that is why mom is fighting that because she knows baby will form an attachment and bond with dad. Baby is and will still be young enough to form attachments to her caretakers for the next 3 years approx. That is why it is important for dad to continue to vigerously exercise his visitaiton and parental rights to the max. The situation in Gramdma's house is toxic, both mom and baby need to be free of that prison no matter how benign the care. I think a GAL will see through the facade especially when mom claims that her extended family is supportive and the GAL gets the true story. Remember, mom is a victim, she has been isolated and has nothing to compare her situation to and that is why she can't handle being a parent when her context is challenged.