Jeep Cherokee Laredo 5.2

Leaked all antifreeze, replaced thermostat,
but if I turn a.c. on it will start getting hot
and leak almost all out again. Can't drive it
in overdrive or it will die, but once you hit
55 mph it drives like a new car. I've
changed transmission filter twice now,
because it would die when put in gear to
take off, at times if I got stopped at a stop
sign, pulling out of a parking lot, etc it
would die in every gear but reverse. So I
would have to put it in reverse then drop it
down to 1st and shift up real fast all while
keeping my feet on both the gas and
brakes, in order to keep it from dying.
That's when I had the transmission filter
replaced and put Lucas in it. I just had it
changed again today because there was a
lot off metal shavings, sludge and it was
black the 1st time and I was told to do it
again in order to bleed the lines. This time
when changed it was a purplish color and
smooth with a lot less metal shavings but
this time it had a few inch long shavings in
the bottom of pan. I've been told many
things it could be.....torque converter,
torque converter solenoid, transmission,
gears, just about everything. I just bought
this about 10 days ago and as soon as it
went into my name, i drove it to a
mechanic straight across from the
courthouse (because the "man" I bought it
from, who said there was nothing wrong
with it, told me to get air in the rear tire
and that's when the antifreeze started
pouring from underneath. I called him, no
answer, left messages, you name it and
now he has me blocked and won't answer
me. There needs to be a law for people
that does this. Because I test drove it, but
only around the block cause it had no
plate, so basically through 1K away, unless
any of you nice people can help me and
tell me your ideas, opinions, advice,
anything. I'm a single mother and it took
me a long time just to save up the money
to buy a vehicle and I get ripped off.
Apparently he does this for a living. But
karma will catch up to him and well, as for
me hopefully it's not going to cost an arm
and a leg to fix it and if it does then I will
have to sell it. But I appreciate any and all
information you all can give me.