Yes, as you said, you need 4x Actiontec MoCA adapters. Technically, using the terminator cap is correct. But as you saw, there is a lock there to prevent unauthorised people from opening (tempering) with the connection. IF, a big if, SCV can accuse you of tempering with their property. You own the outgoing cables from the splitter. The input cable to the splitter belongs to SCV. I have no answer who owns the splitter.
In any case, the splitter need not be changed, so no issue here. The splitter works for frequencies from about 5 MHz to 1000 MHz used by cable tv. Those rated for higher frequency, eg 2300MHz are meant for satellite signals pump through cables. It supplies the same signal (at a lower leve) to each out going cable. The cable connected speed, as claimed by Actiontec, remains at 1G. But actual surfing speed will depend on the total number of devices currently connected.