I recall being in a similar situation-minus the 3 year old. Working full time through full time college, no help with tuition or books or rent, etc.
Blew my tranny at 198k. Threw a rod 1/2 mile after the tranny.
Bought a parts car for $350. Got a 350/350 combo to get by, sold the intake and chrome for $150, and the parts car itself for $75.
Patience and timing (pouncing) are virtues on CL.
FYI- my last machine shop bill for cleaning and honing the shortblock and head work was about $1000 by the time all was said and done. That was 5 years ago- I'm sure it's gone up some since.