An 8-way splitter? Well, that explains why the signal is so weak.

How many feeds out of that splitter are in use? If only a couple, then replace it with a 3-way or 4-way splitter, and the signal will double in strength *without* the amplifier needed.

If you want to install the amp, I'd put it on the input side of the splitter, before the signal is split up.

Cheers