My Saturn won’t start!!! Help

I just bought a 1999 saturn sl2 drove it home
about 20 miles. did a throttle body cleaning to
it got some nasty old smoke out since white
smoke would come out while driving it. The
car was running perfectly fine and no more
smoke.  The next morning it wasn’t starting
up, it was kicking over and sounding like it
wanted to. So my boyfriend replaced the
spark plugs and fuel filter thinking the filter
was clogged since it’s so old. Still nothing,
and at this point the battery was now dead
because it stopped kicking over and started
clicking and the lights were very dim. So I
replaced the battery and it’s able to kick over
again. My boyfriend replaced the starter just
now and still nothing!! He checked all the
spark plugs the starter is on correctly. I’m not
sure what could be causing it now, there’s
some gas in the car about a quarter tank or a
little less. I don’t know how old the gas is so
my boyfriend is going to try putting gas in it
next to see if that helps. If anybody has an
idea as to what could be the issue I’d love any
feedback! Thank you