there is a good possibility that the oil leak is causing dirt and other stuff off the road to stick to your crankshaft position sensor cause it's externally mounted like on some cars,you might try to spray some degreaser around the sensor and clean it up good and look at it to see if it appears broke or cracked,if it looks good try it after cleaning,now your light will not go off immediately if that fixes your idling issue
though i might suggest taking your car to a mazda dealer and having them check it out for your problem cause me being a used automobile dealer i have had numerous mazdas and had to take several of them to the dealer for weird issues of the way they ran or idled and they updated the programming on the PCM and it fixed the problem,if you are in that situation you will spend endless amounts of money to many mechanics that are unaware of things like this like i have till i learned my lesson
as far as you checking your oil level,yes you are checking it correctly,when you change your oil are you putting the recommended oil in it?
as far as the oil light flashing? there is only 3 things i have ever seen cause such,one being the car is losing oil pressure,which if it is idling very low it is possible that might make it flash cause the the pressure is lower than the computer wants it to be so it is giving you a warning,another reason that might make it come on would be the sensor itself is bad or has some trash in it so that it is not reading the pressure correctly,last but not least over the years i have ran across a few oil filters that have been bad and actually would not let the oil go through,not just any one specific brand(the highly rated fram was worst,the cheaper stp also and one other don't remember)
here is a site that is devoted just to mazda 3's(if this isn't it just google this addy and it will come up i am sure)
www.mazda3forums.com
