1998 legacy outback dies repeatedly after catalytic failure / CND at mechanic

[bremsstrahlung]

Hi all! Have been driving a 1998 Legacy Outback wagon w. 262,000 miles. I knew that the catalytic would be going bad because it made a code. I was told to go ahead and keep driving it and that it would take a long time for it to finally fail for good. I drove it for a couple years after receiving this code diagnosis, and toward the end it began smelling very strongly of gasoline. About 2 days after first noticing the strong gas smell, I thought I had inadvertently run down the battery (charging a device), and when attempting to jump-start, it would crank but not turn over. Took a very very long time on the "donor" vehicle (is that what it's called?) and then when it did finally start, it ran so rough I knew there was something serious happening and shut the car down asap. Towed to my mechanic who removed the catalytic parts and by-passed this (making the computer believe that the catalyst was still present -- as my understanding goes -- ??) and I drove it home and it died. I left it sitting for a couple months and then tried 505 CRO and 505 CRF in it. Idled for 15 minutes as the manufacturer directs. When first starting it ran VERY rough and as the CRO / CRF ran through, the idle got smoother and ended up running very well. Drove to mechanic for oil change, and thought it was okay - made several successful short trips in it - to grocery, etc, but then began to die suddenly again, usually when slowing to a stop at low speeds. Back to mechanic - They have done various things to the car, including a filter and pump replacement (they said the filter was very clogged which doesn't surprise me given the CRF treatment.) I do know that the car burned A LOT of oil ever since I bought it and I just replaced about a pint at every fillup. I know that is a bad sign, but I believe the fix for this oil burning was expensive. (Is that right?) And as a Hail Mary I was trying the CRO / CRF. Well, I hope someone can make sense of the 67 or so variables that I have thrown out here, in any case it is a real puzzle for us, and for the mechanic as well. Thank you all -