Having watched the Youtube video, I can see and hear that there are quite a few problem areas with the box:
Leaky pallets- Will need re-facing and properly adjusting.
Leaking bellows around the frames- Will need new gaskets; also checking for other splits and leaks, with proper repairs as needed.
Poor reed response- Almost certainly all the valves are curled and some perhaps missing.
- Will need total replacement of all the valves. Old leather valves stiffen and harden with age and cannot be rehabilitated. It's false economy to try.
- If there is any significant rust on the reed tongues, this will require cleaning first.
- Re-setting of reed plates on to the reed blocks. It says 'screwed reeds' on the instrument, and I see you have noted that there is no wax. The leather gaskets on the reed chamber edges will probably need replacing with new olovisc gasket.
- The reed tongue gaps will then need adjusting and then retuning.
Vox Humana effect- This is a patent device consisting of a weighted leather flap which is designed to vibrate with the bellows air pressure. It sets up the rather odd warbling vibrato sound. Will need an overhaul to get it performing as it should.
Overall, there is a lot of work to do and it needs doing properly with the proper materials. The reed work especially is delicate and needs doing by an experienced repairer/restorer. The instrument looks to be otherwise in quite good condition so it's worth doing, although it will never play like a high-quality box. I would urge you not to try to do the work yourself by improvising with odds and ends of unsuitable materials. The repair work needs to be done using the correct components. Charlie Marshall
(CGM Musical Services) should have everything required.
If you really want to begin to learn how to fettle instruments, obtaining an old one to start with is a good idea, but I would not recommend this one as a starter box for learning to do it. Better to approach an experienced repairer/tuner directly (i.e. in person) for advice or to do the work for you.