Runs rough, spits, sputters and shuts off

I decided to drive the car this summer and it cranks up every time I put it into neutral as long as I don't panic in traffic and try giving it gas, flooding it which happened one time. I got an appointment with a reputable mechanic and at first sight he said vacuum hoses and had me drop it off a few days later. I told him we bought the mechanics manual off eBay and use a paperclip for obd1 diagnostics, and it won't pop a code. He worked on it that day and said it would shut off if left running 15 minutes. It was at its worst when I took it to him! He said the vacuum hoses were fine, no leaks h it was getting plenty of fuel, so it wasn't the fuel pump like older cars before computers. He diagnosed the problem as being the computer itself. But my personal mechanic (hubby) asked him to change the Electronic Ignition Module which was under warranty and for $20.00 he replaced that part, and it runs 100% better. It still has the intermittent hesitation and the fuel gauge started working intermittently again but we're using the trip odometer and fill up when it gets over 210 miles. The lights are sometimes dimmer at night, and I've noticed quirky things going on with it. It still shuts off occasionally when pulling into driveways or at stoplights even though I never let trash get in my fuel and the fuel filter is new. Adding fuel injector cleaner just stunk like awful because the injectors were clean. We're going to change the 3 coils. Then if that doesn't work it's time to replace the computer. It will not show a code the mechanic told me the same thing. Thanks for your help.

The mechanic checked all the vacuum hoses. Last year I smelled antifreeze when driving it and had to top off the antifreeze through the overflow jug. So, now cold weather is setting in and most mornings it's below freezing around 26 degrees right now. I drove it last week to several doctor appts and shopping over the weekend. Hubby poured 1/2 gallon of 50-50 mixed antifreeze into the overflow jug and it sucked it down. Hubby replaced the heater core last summer thinking that might be the problem. It doesn't leak any antifreeze when it's sitting, or leave a puddle under the car after I've driven it and park it. It wont leak down on the ground while it's sitting in the driveway running. However, I believe this antifreeze dripping onto electrical components is adding to my problem. Today I had a dentist appt and drove with heat on to my early morning appt, when I pulled into the driveway at home coming downhill, the car shut off and didn't start back up as usual. I put it in neutral and without the power steering working working, I muscled it into my my parking space and it cranked back up, but before I pulled it in my parking space, it wouldn't crank back up like it always has. Hubby says the antifreeze leak could be coming from the freeze plug, or any other place except heater core. The car will get up to 90 or raster on interstate and run without hesitation. It has power. A rebuilt transmission that's only 3 years old, and I really like my old car and being payment free, and not having to pay collision insurance. Hubby done all the mechanics manual for the Oldsmobile has told him to do, he laid on his back in my gravel driveway working on my car that needs professional help on a lift do to an injury.