Questions about 5kCSQT

[wenode@perelandra.cms.udel.edu (Vinod Arekar)]

I bought an '88 5kCSQT (93k miles) about 4 weeks ago. 
I have some questions about it (most important are first two...)

1. If I pump brakes real fast (prob. not supposed to, because of
   the ABS), the warning light on dash "Brake" comes on...
   is it normal, or malfunction, or some problem with the brakes.
   I checked the fluid level in the central hydraulics and it
   seems to be Ok.
2. Sometimes the ABS switches itself off. This hass happened atleast
   3-4 times. Most of the times this would happen in rain or when I 
   am taking very sharp and winding turns but today it happened in normal d   condition. I'm puzzled. Is this malfunction?
3. I dont have much experience in working on cars, but I'm interested in.
   I saw in Fram catalog that 5kQT has one more oil filter for the
   intercooler. How frequently does one have to replace it?
   How frequently does one need to replace filters on this car (oil/air/gas)?
4. I was planning on using 20-50 oil, is this OK for this car? Any suggestions?
5. There are two gadgets I wither dont know how to use or are not
   working. The memory unit for drivers seat, and the computer. The computer
   shows pressure and "# of miles to empty tank" OK, so I guess it's working
   but how does one reset it for computing avg. speed and gas mileage.
   The computer has been showing 23.2mpg all the time, and I'm actually
   getting about 20 in city driving. Is this too low?

Other than these (minor?) things, the car's great. Great fun in rain
(hasnt snowed so far in Chicago, so havent checked it out!)

Thanks,

Vinod
:wq