I would not get the playset. If you are planning on getting a house, I would wait and buy one for your place. She choose this life without you don't let her make you feel guilty.
Focus on YOU and your kids. Detach, Russ. You have to for your sanity. I know it is hard. I could be in your shoes one day. I know I would be lost trying to date. Can't even imagine it. Be strong and keep moving forward one day at a time.