Those changes are fine; I'd guess the DC line should go with the spells/day listing.
Spells/day: 6/8/7/7/7/7/6/6/6/6; save DC 15 + spell level). The save DCs are Charisma-based.
Excellent. Shall we consider the soul-absorbing ability now?
Starting briefly:
Soul Absorption (Su): If a creature's blood spills onto the ground containing the Tree of Wailing Souls's roots, that creature's soul is absorbed by the Tree upon death if it is on the same plane as the Tree. This ability functions as the trap the soul spell, with the following exceptions.... bit about cutting off the fruit, adding to spell list, include anything about Outsiders, remove curse (or maybe a different spell) before death prevents...
300 ft radius for the roots sounds right.
I'm not sure the original text requires a save, but I'd be inclined to make the save at death (to negate). I'm also not certain if remove curse or even break enchantment is high enough level to counteract this. What do you think?