Hi Zandit, a cheats way is to cut up some high density foam to place under the PUP so that it acts with a bit of a spring action and maybe then you don't need the traditional springs. That is what came with the Custom John Bensons that went in the EX-5 and no springs were used at all.
Alternatively place the PUP where you think it should sit and check out whether there is enough room to squeeze a spring down into the correct location after you have done this next step. That is to screw both screws in a little bit to help create a thread in the timber, then remove one and then see if you can slightly raise that side and squeeze the spring in from the side. If so you can then line the screw up from on top and start screwing it down, then repeat on the other side. Only downside is a lot of the single coil PUP's have threaded base plates for the mounting screws to pass through and that increases the degree of difficulty by a few notches.
For the Humbucker in the Bridge position there will be springs that go under the mounting ring and above the bent metal side brackets and reckon the dirtier black screws on the bottom RHS of top shot will be the ones to use. The smaller screws near the copper tape look like the ones to screw down the Humbucker Mounting ring to the top of the body.
For the snail tape shielding, it can be a quite a fiddly job, especially in tight or cramped spots. Suggest checking to see how high above single coil PUP depths it sits as ideally you don't want to see much if any at all once final setup has been done. Personally I would measure out a length that would circumnavigate the inside of the first PUP cavity and cut that length. Would then peel back 25mm to 35mm of the backing paper and start in the middle and slowly attach it so that in a horizontal plane it sits just below the lip and excess is folded over onto the base/bottom of the cavity, then slowly work you way around until it overlaps back on itself. Maybe you might be lucky in that bottom of cavity could be fully covered but probably not so you have a couple of choices. Either cut out the correct shape in the snail tape and stick that down over the top of the bits folded over in the bottom corner edges or drop a piece if from the top and once smoothed out on the bottom fold the excess up the sides and smooth that down too. Some reckon you need to have solder joins but this method has worked just fine on all of mine with no dramas. Only trap is if the layers get too thick that it prevents free movement of the PUP or may cause things to short out. Obviously there is more room to move in the Humbucker cavity so not as tricky.
Hope this helps.