If you are going to use that spool, you should cut a tongue about 3cm long in the centre of the film. It should go through both slots, and be bent a bit so it won't fall out of the slots.
I thing you are being too kind to the seller of your camera. He said clearly that the meter and self-timer, as well as everything else, worked properly, and clearly this is not correct. When people say "the self-timer sometimes does not work" it means that for some cameras it works all the time, and other cameras it never works, not that it is always unreliable. If this vendor will not refund your payment, he deserves negative feedback.
There are many honest vendors on ebay from Russia and Ukraine. I see that this seller offers a good guarantee if there is anything wrong with the camera, so maybe he is a good guy, but the camera clearly is not as good as promised.
Cheers,
Dez