KIS - you are nearly there.
Please print out a
copy of the drawing above. Then get a pen and cross out 'Distribution Amplifier' and write 'Booster' instead. Then cross out the box marked 'Main HiFi' and the green and red lines going to it. Then cross out the red line at the top going from 'FM' to 'VHF', all the little yellow boxes and the box labelled 'Radio'. Now, there you have it - completely - and that will work. You will even be able to do fancy stuff like record a cable channel while watching different, terrestrial, ones on the TVs.
Using a 3-way splitter will not work.
Really, this is not complicated and you have already done all the hard work by putting the cable in.