I would think about the
risk factors in fixing a car with so many problems.
Is there a chance you'll spend __ months and $x,000 and then hit a wall in time/$$/will to keep working on it? Is this your one project, or just your current favorite of many?
Is there a chance you'll keep going through that wall and finish it, ending up with a car that cost you more to repair than it is then worth? Regardless of whether you got it for free, spent $1k or $10k on it, the question is where do you go from here.
If there are any doubts regarding those issues, then taking steps aimed at reducing risk first, or at least considering risk will be wise. For example, not much risk on the rear suspension - even if you replace everything, it will be less than $1k. Another example - a compression check reduces a lot of risk considering the limited effort involved.
Good luck.
