You're going to have to keep the guitar humidified to keep the cracks closed. If you hang it up on the wall it is going to dry out and the cracks open. Walls are not good places for guitars. If it were my guitar, I'd get it properly humidified and cracks closed up, spray a coat of finish on it and then work hide glue in from the outside of the guitar.
I guess my thinking was that when the first crack occured is was still tight, so by humidifying it until it closed tight again (even if it took only a few days to get it there), then I could then glue it shut, cleat it, and expect it to stay, as long as the guitar is humidified to at least 40% humidity after it is repaired, like it was when it was built. This may be flawed thinking here, so feel free, anyone, to set me straight. Thanks!
Not that you need my backing but I was thinking that I would probably use that approach too. If the crack won't stay closed, than it seems that the top wood is stressed and , perhaps, wasn't as dry as it might have been when the guitar was built. Now the wood wants stay in the "place". Splinting it should insure that it doesn't crack again.
It was either Sloane or Ibex who made (or still makes) a little brass jig with sandpaper to shape a crack splint.
Picture two small plates hinged together at the bottom, forming a variable "V'. The sandpaper is on the inside of the 'V' and the angle can be locked. A small piece of spruce, the length of the crack+, is drawn-through the 'V' and eventually sized-down to whatever matches the vee-cut you made in the top with a razor knife.
The angle of the 'V' should be as steep as you can get-away with. The splint is glued-in and cut down to surface when dried. Works pretty well but takes some practice.
Our winters are very dry so January and February are very busy months for me repairing cracked tops and loose bridges ...I usually cut splines by planing one edge on a slight angle and then cutting the other side with a sharp knife using multiple passes.
To get glue into a crack I put a bead of glue over the crack and then clear packing tape over top sealing around the glue, then I rub the glue into the crack, it can only go into the crack. There are some old finishes that will lift with the packing tape so use your own discretion.
I make cleats using a small plug cutter and then thin them out. I place them by putting a rare earth magnet on the outside and securing it with masking tape. I then use paper glue the (kids stuff that comes in a tube like chapstick) to stick the back of the cleat to the second magnet and put fish glue or wood glue on the top. Reach inside the guitar or use a tool to get it opposite the outside magnet and it will jump up into place.
Regarding humidity I keep mine on the low side in the winter assuming that the guitars that come in are going back to less than ideal conditions when they leave and a sudden big change in humidity is worse than a small one.
If this guitar was on my bench I would spline the crack. I've used shaving from a hand plane as spline material too.