Re-Bath didn't settle with me so I can tell part of your story. I remember seeing large cracks around the tub that were dobbed up with caulking and I remember you saying one of the cracks was 5/8" wide.
Yours is not the only complaint about Re-Bath we have heard, the complaints are many and troublesome. We had someone come in and refinish our cast-iron tub and it looked really good.....for a few weeks. The have re-done th job 4 or 5 times and it still peeled off again in the bottom of the tub. The sides and outside seem to be holding well even after something like 10 years.
What I am saying is, if you're going to spend the money, get a new cast-iron tub and have it installed professionally. Then have a professional tile man to come in and re-do the tile. You'll be glad you did and you won't have to worry about fit or match or any of that stuff.