If or when you end up living with this other woman, I'd start having weekly sit-downs where all three adults check in with each other to see if everyone's wants and needs are being met -- and if they're not, to brainstorm as a team for ways to correct the situation.
There's no reason why everything has to be perfectly balanced all the time. People are complex and relationships are imperfect. Embrace the imperfection; it's your way of being uniquely you.
But yeah, communication. A whole lot of it. And get better at it with practice. Trying to read people's minds (e.g. seeing signs of trouble) is much less efficient than is simply asking someone outright how they're doing and what they're feeling. Make no assumptions and take nothing for granted. Too much talk is better than too little, especially in the early stages.
You might want to keep a three-person calendar too. But like the others were saying, consider dating for awhile before moving in together. Sometimes moving in together goes smoothly but in most cases it's really hard work and takes a lot of adjusting.
Hope these thoughts are helpful.
Love means never having to say, "Put down that meat cleaver!"