Which screws and mounting option are safest for installing a children’s Swedish ladder?

[theateist]

I’m trying to mount a Swedish ladder. The mounting holes on the brackets don’t align with the wooden wall studs: the studs are 16'' apart, but the bracket length is 29''. I was advised by user "Half-fast eddie" to put the brackets on the outside of the uprights and they will align with the studs like this:

However, I found that the studs are not straight. I drilled small holes to verify, and basically the left stud is at an angle, so I cannot align any bracket with the center of the stud. Because of that, instead of drilling holes in the brackets, I think the easiest solution would be to use the plywood idea suggested by user "Nealtw". However, instead of plywood, I was thinking of installing four horizontal 2x4s or 2x6s (or something else, if you think there is a better option), secured to the three in-wall studs, and then securing the ladder to those horizontal studs.

I can secure the ladder to those horizontal studs in one of two ways:

1. Use Simpson Strong-Tie angle brackets to connect the ladder uprights to the horizontal studs, which would eliminate the alignment issue (image 1).
2. Attach the four factory wooden brackets (which is 30''x2.9''x0.4'') that came with the ladder to the back of the ladder uprights, and then screw those brackets into the horizontal studs (image 2). The upright is only 1'' and they provide 1.75'' x 0.14'' screws. I have 2.5''x0.19'' T-25 GRK cabinet screws.

Which option would be more secure? It seems that option 1 would be the most secure, but it is much more work and requires dealing with angles. Option 2 also looks secure, since I do not think the manufacturer would suggest it if it were not, but I am concerned that because the upright is only 1 inch thick, it might split when I drive in the screw and the factory brackets are too thin (?) 30''x2.9''x0.4''.

Additional question: regardless of which option I choose, would 2.5" x 0.19" T-25 GRK cabinet screws be sufficient to secure the Simpson angles or the factory wooden brackets to those horizontal studs?

OPTION 1

OPTION 2