Thanks for the kind words!
To answer your questions:
1: Currently, you would indeed need to have one master in one region, but you could have RDS read replicas in other regions. With Amazon RDS, you can create a MySQL, PostgreSQL, or MariaDB Read Replica in a different AWS Region than the source DB instance. https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.html#USER_ReadRepl.XRgn
You can also do multi-master with Aurora (in preview only) within one region https://aws.amazon.com/about-aws/whats-new/2017/11/sign-up-for-the-preview-of-amazon-aurora-multi-master/ and we have announced multi-master multi-region for Aurora for 2018 — which should solve the last piece of the puzzle.
You can read more about that in my previous blog post in this series: https://read.acloud.guru/why-and-how-do-we-build-a-multi-region-active-active-architecture-6d81acb7d208
2: Deploying a lot of services is always the one thing that is tricky… but I personally like splitting things into micro-services — and if I would add 30 lambdas to handle my 30 APIs — my template would just be longer :) I would also use AWS X-ray to help me debug. As for Express, check out this project: https://github.com/awslabs/aws-serverless-express this might help you get started.
Hope it help — let me know if you have more questions.