From a quick glance, it sounds like you have many tools to support another child and you are giving this a lot of thought before acting. If only MORE people would consider their career, financial stability, home life, physical and emotional capabilities before getting pregnant... I think you're actually doing things in the correct order and doing your best to set up as successful of a situation as possible for a potential child.
I know of someone who chose to adopt as a single mother. (I'm not saying this because I'm suggesting that's what you should do; I'm saying this because I know of her situation and how wonderfully being a single mother has worked out for her.) She was established in her career as a lawyer, had her own home, had financial/emotional/physical support and security. She also knew that it would be unlikely that she would be finding a mate and settling down anytime soon, yet she knew that she wanted to form a family. Thus, she adopted from Guatemala. For her, it has been one of the best, most rewarding choices she has made in her life.
I think putting this question out there for people (or people who know of people) who have gone through something similar is a great place to start gathering feedback for your decision-making process.
Search your heart and good luck with whatever decision you choose to make! I'd love to hear updates!