Why won't my 1996 cadillac seville start after the obvious?

My husband had expended his
knowledge on our car and replaced
(in the past three months) the battery,
alternated, and just recently to no
success, the starter, manifold
gaskets, and the battery cables.  He
had also changed the oil. The car has
very low miles (under 40k) and was
running wonderfully. Three days prior
to replacing the starter it developed a
hot bitter near wire burning smell. No
fuses appear to be bad ( although I
could not list what he checked)

The car has said to 'service
emissions system'.
The peculiar thing is that initial day it
happened we thought it was a dead
battery ( again after the alternated
replaced) and just wouldn't take a
charge. Husband took it in and they
said it (new battery) was fine. Putting
it back in the car he got it started and
drove it home (about 2miles) and the
next morning dead as could be.  
Knowing the battery & alternater are
fine it had to be possibly the starter.
The men at o'riley tested the starter  
said it was fine. We replaced battery
cables on old starter and manifold
gaskets- still wouldn't really turn
over, decided to buy new starter and
same thing wouldn't really turn over.
It tried harder each time but the 4th
try smoke coming from the starter
area.  Any clues? Unless I get
feedback I have to spend a ton I
towing and labor which I'd like to
avoid if possible.  Thanks!