Just read your list of problems The first fault (Diagonal lines & picture collapse from left & right) Sounded like either A poor connection or dry solder joint either on scan coils or scan coil plug / socket on main pcb.
If this were the case the engineer that called out should have spotted this & sorted it very easily. But you say it is still the same so what did he do ?
Did he give you a reciept with break down of what he did ? If yes please post it here for me to go over.
The sound problem you describe has thrown me a little so could you please post your tv model number on this page so I can see if this is a stock fault.
The static shocks you are getting is relatively normal & not a problem unless you are getting them off of speaker grilles or even tv casing if it is silver in colour.
I am UK based & have access to samsung technical but I will need your tv model number.