Oh, if its 102°F then no more than 10 mins. I usually take luke warm baths even then I don't stay in long. Or just dip my feet/legs into the spa. Babies can't regulate heat yet, so the lower the temp the better for them
Try Epsom salt in the water. It'll help with the soreness. It just adds magnesium to the water. I know magnesium sulfate injections are common to prevent pre eclampsia so its not bad to just soak in it. I use magnesium oil daily applied externally for nausea haha
As long as the water isn't too hot, it really shouldn't matter how much time because bath water cools off unlike hot tubs that remain at that temperature. Just make sure the bath isn't extremely hot... Just a warm bath works! Or you can try getting a heating pack too! Like the rice ones. They're amazing