Ok, a huge red flag is that you have discussed being together apparently earlier but not acted on it. You say because he was in a relationship for 10 years but it’s a relationship in which he was mentioning that he could be with you. So you’ve either had a very long emotional affair or you’re his backup which would suggest you have always fancied him but he was in this relationship. He picked up on your feelings and kept you just interested enough that if his relationship ended you would still be available to him. I imagine every time you got somewhere with a guy you were seeing that he wouldn’t like them, he might get a bit withdrawn or maybe a bit sulky? It’s because he thought he was losing you, even though her didn’t want you enough to end his relationship.
He will still go ahead with being the donor if you aren’t able to have a relationship? There is generally a reason why people use strangers for donor conception it’s because they aren’t made to compromise with someone who they aren’t in a relationship with and could never be in a relationship with. You could get the ick with him when you meet in person but you’ve agreed to have a child with him. So you’re going to coparent with someone who gives you the ick and have to compromise what you want to meet them. If you used a stranger you are going it 100% alone but that also means you don’t need to compromise with someone you don’t like.
However, you like him more than you are willing to admit so you won’t see these red flags. So, as the relationship is inevitable, I would recommend not moving to Australia/NZ with him and getting him to move here and not just because of the legal implications that you won’t be able to bring your child back home if the relationship fails. If he’s supportive and gets it from raising his step kids, he’ll get why you want to stay near your support network. Although he won’t have done the early days with his step kids.
Having a baby can be really isolating. I live 4 hours from my family but in the same country. I’ve lived here for 10 years before I had my DD and 5 years in my specific village. I had local friends, I knew of walks, activities, coffee shops, I know how to drive around, i know how to get places, I know how the doctors work, I know the area and my life is here. I have a supportive DH and a village around me of people who I knew could drive me to the hospital if needed, who could take care of my dogs, who if I was struggling could come and watch DD for me. I also have a really great group of NCT mums locally. It was still the most isolating time of my life. I hated my job but I couldn’t wait to get back to work, to normal.
Now you’ve said your mum has the means to fly out regularly but that doesn’t mean she will. You have a sister and she has two kids here. So how long are you happy to not see your mum? At the very worse case scenario if your friend doesn’t allow you to leave the country with his child but your mum can’t make it over, how long are you prepared to not see her? For your child to not see her? When baby has first been born, how many weeks old do you want baby to be before they meet your mum? My mum lives 4 hours away and DD was still 4 weeks old before my mum met her. With international flights this could be longer. Are you happy with that? What if someone in your family gets sick? I’ve done the cross country dash when I’ve got the call, it’s the worst drive ever. How do you feel about your mum getting ill and you having to sit on a long-haul flight with a toddler who is picking up on your emotions and your stress? How would you feel if your mum was dying and your friend wouldn’t let you leave the country with your child to say goodbye to your mum.
Let’s imagine a very likely scenario of baby getting a bug and they’re not eating or drinking, which happens a lot. They have a temperature and they’re becoming dehydrated, they’ve not had a wet nappy for some time and you’re getting worried. It’s only 3pm your time, your partner is at work but it’s 2am UK time, you can’t ring your mum. Maybe you don’t get on with his mum, again it’s common, so you want a night out with your friend/partner but you’re not comfortable with MIL looking after baby. Who is going to watch the baby? Are you going to wait until your mum might be coming over to have a night out? I struggled to establish breastfeeding and needed support from my DH and when he went back to work, I needed that from my mum. If you have something similar to me are you happy to try breastfeeding in front of his mum. Constantly trying to get a baby to latch, crying in front of her and possibly opening yourself up to judgment. Then pumping in front of her? That’s what I had to do in front of my mum. I had to do it every 3 hours. I really get on with my MIL but I wouldn’t have wanted to be that vulnerable around anyone but my mum and DH. What if you need a c-section and need help after the birth? Do you want your mum for that?