A/C not working properly

When the A/C is on:

There is a rattle that increases with raised setting (low to high).
There is major drag in acceleration (i know this is normal to have a small drag because the A/C uses power but this is major drag).
It obliterates gas, I actually thought someone was siphoning gas when I first noticed how quickly it was dropping but it's just the A/C, for 1 mile of driving if the A/C is on it blows about 6 miles worth of gas (i noticed the major drop in my mpg about 3 months ago and it is now half of what it was a year ago, I have a digital gauge as well on my dash and used my GPS in correspondence with watching the mileage left and that is about what it averaged out to)
Sometimes it will blow cold/cool air if it isn't too hot outside, but when it is hot or during hotter parts of the day like afternoon it blows like a fan and takes about 8-10 minutes to get cold(this doesn't happen every time, but at least half the time)
i should mention just over a year ago (in march 2018) the A/C started acting funny, sporadically for about 2 months then every time for about 3 months it wouldn't cut on unless I hit the steering wheel or top of dash(like a half slap). Then around September the A/C stopped blowing completely, the compressor still kicked on and it was still making cold air that you could feel if you stuck your fingers in the vents but it would not blow. We took it to 3 places and none had an idea of why it wasn't blowing because the ones that actually looked said the fan and switches looked fine, then about 4 months ago it just turned back on. We didn't do anything to it since we didn't know exactly what was wrong so I don't know why it stopped or started working. The rattle sound has been there for about 2 years, very slight at first then got worse when it started cutting out. That's also when the other issues started and were all slight at first but now are pronounced except for the gas guzzling, I didn't notice that until 3 months ago