This post is very antagonistic but I can say that point 3 rings very true, even using advanced/data heavy SQL got very annoying for me relative to SQLAlchemy and I don't think you really want to try and pull it out.
It's been a while since I've used SqlAlechmy, but I remember absolutely hating it. Like you said, Django's ORM fails above very simple manipulation and even though SqlAlchemy might be better, it was still awful. I found it better to just write raw sql for my few use cases than to dive into page after page of sqlalchemy documentation.
I second to this, SQLAlchemy was nicer to use when my data model wasn't super simple and used PostgreSQL specific features.