Noises problem
1996 Mazda MX6 6 cyl Front Wheel Drive Manual 231000 miles

Help, my mx6 is making some weird noises

Here's the situation:

I changed my oil 2000km ago(it's now at 231,000) and put 4l in. We checked the dip stick and it seemed like a good amount. After that I was driving around and noticed the car to be a little sluggish. So I stopped and let the car settle and checked the stick and it was down low, so I put another litre in and was wondering why a litre of oil dissappeared in like a week. So I kept driving and a few days later I noticed this whooshing sound coming from the car, but it only makes the sound when I have the gas more than halfway on or when I'm flooring it through the gears. It's almost like it is going whoosh, whoosh, whoosh very fast repeatedly as I keep giving it gas. Then my muffler broke off from my exhaust and needs to be welded back on. Now the sound is rediculously loud since the muffler is off, and the car has a loss of power.

So I took it out my friends house last night and drained all the oil out, and guess what. There was only 2 and a 1/2 litres of oil in the engine! where did it go?? I put 4 litres in when we changed it and another litre in after it went low again. I know that is a very high amount of oil for a car, and that might've been the problem in the first place. But now the car is sluggish, has a whooshing sound everytime I give it a lot of gas and oil is dissappearing? I put 3 1/2 litres of oil in last night and have it sitting in my yard not wanting to drive it. Does anybody know what the problem is? Thanks, I need help!

Also, we were under the car trying to take the oil plug out and noticed the oil filter was covered in oil and the hose connected to it was wet as well. Could it be a slow leak in the oil hose or maybe a bad filter? Also, when I took the oil out of the car last night, it looked like it had 10,000 km on it, it was very dark and it looked worn. It was only 2000km old!