To be honest, I think the only universal motivator to adopt is 'I really want another child'! If you really want to be a mum again then adoption might well be exactly the right way for you to go about it
You do need to make your head and your heart have a serious conversation with each other, and get mostly in line with each other. Sort out how you really feel, about work, freedom etc, so you are totally comfortable with all the things involved in parenting a younger child again
Don't be swayed towards IVF if you definitely aren't interested. I do believe that if you have a desire for a biological child, then you should persue that, because you need to be absolutely committed to adoption. But if you truly aren't interested in having another birth child if you could adopt, then it's all fine. Apart from the nosy people. Ignore them/think of good responses to shut them up
Adopting to give a child a playmate would be a bad reason, but clearly you don't feel that way. Everyone who adopts, either after having a birth child, or adopting their first child, will have concerns about their existing childm and what they can manage in light of their existing child/rens needs. I've never had a birth child but adopting for a second/third time gives you the same concerns about how your existing children will cope, what you can manage as a family etc. In my experience, most people do let their existing childs needs be a big guide in deciding what kind of child to adopt for instance, what needs they can accept etc
I don't think your hopes are unrealistic either. You hope for a generally good family life, but are prepared for some of the issues a traumatised child might have, like the issues you've seen your friends children have, and you are comfortable with those issues. Unrealistic would be hoping for a child with zero issues and zero problematic background factors. In my experience, the majority of waiting children have some issues but not major issues. So, food issues, sleep issues, insecurities, are all very common. Other common issues can be social/making friends, speech and language, some developmental delays etc. You do have to be realistic that its not always possible to identify a childs needs pre placement, and sometimes a child will display difficult behaviours you didn't realise they had. But I personally know many happy families whose children have issues but that doesn't stop them from having a good family life. They do have extra things to consider, sometimes have to parent in a different way using different techniques than you would for a secure child, more forward planning involved with certain things. That doesn't stop them being absolutely glad they adopted and unable to imagine life without their precious children
My son, for instance, is 8 now, and came home aged 23 months. He has had, still has, some insecurities, trust issues, seperation anxiety, sleeping problems (these are mostly in the past now), and problems making friends. He used to struggle in school a lot but has now caught up and he is actually very happy in school right now, which is great! He is an absolute joy :) I have to plan some things carefully and use forward planning (eg. invited to large family gathering, i know he's going to struggle with that, what can i do to help?), use some different parenting (no time out, but quiet time with mum instead), do things i wouldn't necessarily need to do with another child - he might regress slightly and need more babying, rocking on my lap, he needs to excercise away his nervous energy as he can get very hyperactive when anxious so masses of outdoor stuff, he struggled in reception/Y1 because he had a deep fear i wouldn't come and pick him up at the end of th day and he'd been abandoned, so I sent him to school with a hanky smelling of me (I sprayed it with my perfume and wore it on my skin for a couple of day before giving it to him) and a possession of mine to look after for me, and it made him feel much more secure. Just some examples of parenting a child like him. Things that don't prevent us being a mum and son who adore each other, and wouldn't be without each other for anything :)
My older ones do have/have had very significant issues, but again, I don't regret adopting them for a second, and I do feel that we are a positive adoption story, a success story. They have a mum, a family. It's not easy, it's been and is incredibly difficult sometimes, but it's worth it. I do think though, that since I chose to adopt older children whom I knew had histories of abuse and emotional and behavioural problems, that I'm not really the best example of an adoptive family to give to someone who is thinking of adopting a younger child without (known) significant issues. It is of course possible that a child adopted young could go on to develop significant issues a few years down the line, but for me, a bumpy ride and challenges was always a certainty, not a possibility. So I think my sons story and my life with him is the best thing to focus on, because it's just (IMHO) much more likely to reflect your situation if that makes sense.