This is what needs to be changed/updated
You will need to re-evaluate your AD design. Both companies have their own Active Directory forest. You cannot simply move a domain under one forest to another forest. Your either need a trust or use AD merge tool
After you correct the AD design, you will need to better explain the trust relationship. Trust can be setup with different “ways” that is based on the direction of the trust.
You need to detail FSMO role placement.