1. If signal is fine at the tap and the drop to the house is less than 100 feet your loss (RG6) be around 4.9db @ 550 mhz.
2. Your cable footage to the split is small but the total of your cable run could take another 2.5db not counting the split.
3. The splitter would be a big factor. the furthest cable run should be connected to the 4.5 db port. The others will have the 7.5db loss.
4. If the TV sets have converter boxes then they may need +10 db input to work correctly. If direct to the sets only then 0 db is preferred.
It sounds that you are loosing too much signal and what is the output at the tap? Some companies only are concerned with tap out put @ 550 MHz to be 12 db. You do the math and you may find, if the connectors are done correctly, the problem may lay that the output of the tap is not enough. The cable company sometimes can correct this by changing the base plate to a lower value. Post what corrects your problem.
Good luck.
