I would say No it is not worth rebuilding, which as a Bianchi fana nd owner of a '87 Sport SX really hurts me to say.

1st of all would the complete bike fit you? It looks like a pretty small frame maybe a 50cm, I don't think it is a 53 looks smaller.

The Sport SX was a solid lowend 'Sport' bike which was aimed at guys who needed an affordable bike for fast weekend group rides but not really looking to race. I love the way mine rides and this one has a bit nicer ful ChroMoly frame sos hould be a better rider.

The '88 like this one (though you were very close guessing '89) came with a shimano Exage Sport group and I think freewheel sill at this level but don't remember for sure.

Unfortunately you just don't seem to have enough parts to make a whole bike and by the time you collect a BB, crankset, seat and post you could likely pickup an complete bike just as nice.

The part that worries me the most is the frame/dropout damage. can you post a pic of that? I have seen in person and here some frames with repaired dropouts and if done correctly should be OK. However you description of needing to put a washer between the locknut and the dropout worries me. Most locknuts are serrated to grip the dropout to hold the wheel inplace, and putting some spacer in there prevents this.

Some of the parts do look pretty nice. The brake lever look like DiaCompe something and likely are the matching levers for those good looking DiaCompe brakes. The CampI will likely generate a few dollars or decent trade items even being just a Gran Sport.

I hope this helps.