Characteristics of this attic and what can I do to make it easier to traverse?

Those are joists and the measurements center to center can be all over the place. I'd stay away from AtticDek and install plywood instead. If your attic access allows you to get 4' x 8' sheets up there, great. If the boards are too short by an inch or two going across the joists, sister a 2x4 to the joist. If too long, then cut off the excess. If your opening is small, just measure and cut the plywood down below, then bring it up. With those short distances, 1/2" plywood will do the trick. To secure the plywood down, use screws to avoid pounding and possibly cracking plaster or drywall seams. Be careful not to screw through any cables.

The code requires ceiling joists support a “live load” of 5 lbs. per square foot plus (psf) a “dead load” to support the joists, insulation, lights, etc. This usually adds up to 8 - 10 psf depending on the size of the joists, depth of insulation, quantity of lights, etc.

Just looking at your attic I’d guess you’re at the maximum span already. If you give more info we could calculate how much storage could be added. Like: size of joists, span of joists, species (or where you’re located).