RF wiring

I am going to re-configure the RF distribution around my house to improve the reception to the TV in the kitchen. I want to replace the 4-way splitter I have in the loft with an amplifier and I also want to rearrange the cabling between the lounge and dining room, I will need to use a 2-way splitter for this.

My questions are;

Will I need to ensure that the cable lengths are equal for the 2-way splitter and will splitting one cable into two reduce the signal strength?

Will replacing the splitter in the loft with an amplifier improve the RF signal?

I have NTL Digital, the RF output from the STB has an attenuator fitted, will removing this attenuator improve the picture quality on RF or should I leave it alone?

Thanks for any advice.