Doesn't sound good... I would say the combination of symptoms you describe point to a bottom end failure, although it would appear to be main bearings rather than big ends. Do you know if the engine has had any major work recently? (big end failure is not uncommon- did the seller slap a set of shells in it and hope for the best?) I guess it was a private sale (no warranty)?
Basically, the only way to economically repair this car would be to fit a good secondhand engine. But before you commit, it would be wise to have a very good look at the rest of the car; these cars have a number of known issues, and you could very easily end up spending way more putting this car right than buying a good one in the first place. There's loads of info on this site, but I'll give you a few hints to start with: check the condition of the radiator, front wishbones, rear suspension bushes, exhaust, and brakes (especially the rear).
Sorry to say it doesn't look like your Alfa ownership has got off to a good start. Good luck!