nicktheplumber
As regards question # 1: you can’t use the “saddle” (puncture) valve to tap into the PVC line. Such valves are for copper lines only, and usually malleable/flexible lines.
As regards your water pressure (and from your post I assume you have a well and pump), you may have had an undersized or defective tank, and replacing it may have corrected your problem. However, if you still have the problem, it is most likely due to either occluded (galvanized) or otherwise undersized supply lines, or to water-saving flow restrictors at the showerhead. If you have a bathtub with a shower diverter valve, and if the bathtub spigot provides ample flow but the showerhead doesn’t, then a “low flow” showerhead is your problem.
You sound like an intelligent guy for asking these questions, but your questions about using a “saddle valve” on PVC pipe indicate that you are relatively uninformed about basic plumbing technology. I would therefore suggest that you consult a licensed plumber.
NtP
