The squeak when lifting the vacuum is perfectly normal, as you are applying pressure to a part which has slight movement in it. As for the other noises, It’s hard to diagnose a noise without actually hearing it for yourself. If there’s any way you can upload a video, (you’d have to upload to YouTube and then link it here), that would help, if it were possible.
The way you describe the sound changing from start to finish of cleaning, could even be the filter becoming progressively more blocked as time goes on, which could be caused by the reasons stated in previous replies. I’d say it is bound to be an issue with the cyclone or bin, there’s not much else it can be, (and you’d no doubt have to change the filter at the same time too), however as you rightly say, those parts are pricey, and account to a substantial chunk of a new machine.