Have you tried Miralax at all? You say you alrrady have soft stools, but this has been the only thing that consistently allows me to have pain free bowel movements. My doctor said it's safe to take everyday, but after my own research I noticed that there aren't really any studies done on it so I try not to use it more than necessary. That being said, I do use it when things become unbearable. Since you are so close to delivery, maybe you could just use it for a short time to try and heal up before delivery? I've tried so many other things and this honestly worked like a miracle for me.
I thought about trying the dilation for a while but never really ended up trying it. If things are tight at first, I'd try a hot bath and then lying on your side in bed (if you already don't do that).
Do you have spasms too or is most of your pain during a bowel movement? While I was breastfeeding, I'd be in pain for most of the day but I'm not sure if I was having spasms or just general pain from it being torn open. Currently, if I'm careful, my pain is mostly limited to bowel movements. Definitely not looking forward to breastfeeding again :/