'94 Altima 2.4.L just quit on highway and turns over , but won't start has spark, fuel, intact timing belt

The Following are symptoms that I noticed as my 1994 Nissan Altima (160K miles) with a 2.4L twin
overhead cam engine started to fail and ultimately quit
• On  local shopping trip, I noticed green fluid (antifreeze) on the pavement coming from my car’s
waterpump.
• Within maybe ten miles I noticed a decrease in engine power especially from a stop light. It
didn’t have its normal pick-up (during this time period I was monitoring the cooling fluid and adding  
water as required and planned to change out the water pump.
• The temp gauge never got above halfway between ½ and full overheat. So I suspect the temp
gauge is faulty. I did remove the thermostat from its housing thinking it may be stuck as It’s not that
important in S. Florida
• We suspected a blown head gasket and isolated the problems to be #2 & #3 or the two center
cylinders . May have I will have to mill the head flat as well. The sparkplugs indicated water or coolant
had escaped into those two. I put Barr’s head sealant and followed the directions closely. I drove the
car about 20 miles a day for the next couple of days and by the way, I put a bottle of ground pepper
into the radiator and that seemed to stop the water pump leak, but still planned on getting a new
pump soon. Checked oil for water in lube oil and none noted.
• After about 3 or 4 days I was on the interstate and monitoring the temp gauge which was
holding right in the middle, but also notice a definite loss of power and struggling to get up the
bridge slope and exit on the other side, we made it over the crown of the bridge and then suddenly
with no noise, banging, rattling or lurching the engine just quit at 50mph on an off ramp the engine
stalled and all the idiot lights came on. I pulled over on the side of the road and waited for the engine
to cool to add water, but the engine wouldn’t start and sounded like it was just spinning with no
compression. I towed it the next day home.
• I’ve lost a timing belt before and thought that may be the problem. I popped the cover that
exposes the cams and timing chains, spun her over and the chains seemed fine, no water in the oil,
had spark, fuel and fuel pressure. However, the rubber collars on the center spark plug lines were very
melted and disfigured so they make me believe I still have a gasket problem at minimum, but don’t
know why engine won’t start , we even tried starting fluid?