Hi and welcome
We did pretty much the same thing, although we know my partner is polyamorous. The whole deal started and finished in three weeks. You should read the second link first that deals with making it happen. Trying for a Triad is the break up and the pitfalls.
You're lucky that your guy lives a long way away because there is hopefully less likelihood of the parties falling in love. Just be careful, we hurt a very nice lady quite badly.