toilet flange spacer for new floor?

Hello. I'm just a home owner and not a professional plumber and I hope someone has an idea on what could be causing this problem. I just bought a Whirlpool portable dishwasher that works great if it hooked up to the sink faucet as designed. I really would prefer to not have to pull it across the floor but have it plumbed kind of like built in. We have an old house with little kitchen counter for a regular built in dishwasher. So I have it sitting over against the wall with the factory drain and supply hoses disconnected and stuffed underneath the chassis. I have an aftermarket drain hose connected to it and running through the floor to a utility sink in the basement. I have a aftermarket 48" dishwasher supply line with the L-shaped faucet connector hooked up to the dishwasher inlet and running through the floor and connected to a 1/2 MIP adapter on the 3/4 Pex house hot water line. This machine is not getting much water at all when I run a cycle. The rest of the house has great water pressure even the upstairs bath that is connected to one side of the 3/4 Pex tee that the dishwasher is connected to. As I said at the beginning of this long winded post the dishwasher works great with the factory hoses connected to the sink. What could be causing this machine to not get enough water to run? There is a faucet supply line under the faucet that is probably the same size as my aftermarket supply line but the machine gets plenty of water when it's hooked to the sink faucet. I am stumped?

I live in an older style 2 story house. What I believe is an old cast iron drain pipe that runs from my basement through the roof is behind plaster wall in my living room. I noticed a dripping sound inside the wall when my son was taking a shower. So I stopped using the shower up there but recently heard it dripping when the toilet was flushed. So I am guessing the problem is with the pipe itself and not the shower drain or the toilet seal? Hopefully someone understands what's going on here and can give me a tip on how to assess the situation.