some tech questions

alright, well for the past months my check engine light has stayed on for one month, then turn off. turn back on for another long period of time and just last night it turned off. i checked it using the tool and it said its the 02 sensor (i think the primary one). my idles are not bogging and car seems to be running normal. the only thing i notice is when i rev it up, the rpms seem to stop very abrubtly (say i rev it up to 4k, it seems to stop exactly at 4k like it hit a stone or something. it just doesn’t seem like a smooth stop). not sure if thats normal but anyways, i gased up last night to 1/2 tank and now today after driving less than 50km i am almost at the 1/4 mark (i usually get 100k + for each 1/4). if my 02 sensor is the culprit, would that cause my crappy gas mileage? (i havn’t gone past 5k rpm)

and one more simple question while im at this post, if i want to get rid of my abs, do i simple pull the two abs fuses in the box and thats it?

any information would be greatly appreciated. thanks