I suggest .15 to .2 mm layers and 3 to 4 perimeters if you are using a .4mm nozzle. 15% infill is enough for the tower. I printed the holders with a higher infill- I think it was about 30%.
I have provided two options for the tower. One without supports that you can add your own supports to as you like and one with my support structure. The tower probably can be printed without supports though at this scale i would expect the top of the arches to be a bit messy.
Remove supports from the tower (if you used my supports). I worked an exacto knife between the supports and arches and carefully cut & worked them free.
Glue the holders in place. The top holder was a good snug fit for me, but could be a bit tight depending on your printer.