First, K's arcade is great with usually fast shipping, I've bought several ribbon cables from them along with various original boards that a lot of other pin sites always seem to be out of stock on.

Second, the lines are usually caused by incorrectly seating one of the 4 contact cables from the MPU to the DMD controler, if you are off by a pin, or as sometimes happens a whole row, this occurs, I'm just saying that the cables may not be bad, you might have miss aligned one of the connectors on a board.

Third, your switch error, when you go into test hit enter once to see the error report, I think you have a hand opto failure (mine was the "THING up" opto had failed). If both up and down do not register the game will not let the subway lock up switches report as closed if the ball is locked by THING.
If you have a failed opto on the thing opto board, K's has/d them in stock awhile ago, or you can desolder them and replace them with a flipper opto board pair, if you have a a spare one laying around.

Things Optos are the black U shaped optos and are soldered to the circuit board, if you are not handy with a desoldering gun you will probably destroy the board while trying to remove them. A new thing opto is about $40 pkus shipping, if K's dosent have them in stock marcospec.com might.

Good news about the scrambled video and sound though.

To remove thing, you need a helper (dropping the playfield on the back of your head SUCKS) to hold the playfield while you unscrew the large metal box. Disconnect the molex connectors that go to thing and the opto board. Remove the hand assembly. Remove the metal collar with the tab that blocks the optos, remove the old board, replace with new board. Replace the opto collar, I usually put it back on the lower opto pair since the hand is usually down when you remove it.

Reverse process to reinstall.

Also, what Terry B said...

I believe that 72 to 74 volts at the flipper coils is about normal/average, mine reads about 72.5, my IJ reads 74.
As far as the fuses blowing, you could have a bad diode on the flipper coil which causes all kinds of problems (melted coils, blown drive transistors, and all around general nastiness) or a problem with your Fliptronics board, or you might have wired the hold and power wires backwards (I've done that a few times too many myself)

Do you have the leaf style switches, or the "newer" type one opto switches? If you have the newer style switches sometimes the plastic/metal interrupter sticks on the optos and partially blocks it. Also make sure the little return spring is not worn out or detached.

Very strange, glad it worked out.