1995 sc400

Fill up at Arco about a month ago and the car started performing poorly. Low/rough idle, sloggish, low power, stumbles around 40mph if you try accelerating. Idles like a truck (put-put noise).

Replaced external fuel filter with no difference. There was rusty appearance to the fuel and particulates ahead of the filter (after passing thru filter).

Tried a cheap ($40) scanner but the CEL blink continuously.
Tried an expensive ($230) scanner but "Unable to connect to vehicle's computer" was the response from the lcd screen. I checked connections, retested etc. with no change.
I jumpered E1 with TE1, TE2 & TC. TE1 gave the same continuous CEL blink and the others made no difference.

Diagnostic connector under hood.

1. How can I tell if the car is OBD1 or other?
2. Is the above CEL response normal when there are no codes?
3. Any ideas what's ailing the car?

Thanks,
sch