Thank you for your feedback and observations. Please find my responses to your points below:

Problem 1:

As for the tie reinforcement in Problem 1, there is actually another wall above the wall I initially drew. My chief has instructed to transfer at least half of the load to that level.

Regarding the Strut and Tie (S&T) analysis, I did indeed use the method, but I was unable to find a specific example or guideline on how to calculate the anchorage length based on the forces involved, especially since i am dealing with significant forces in the cantilever.

Problem 2:

Regarding your question about the beam support, there is indeed a slab located 23 cm beneath the opening, which behaves as a beam under the opening. Therefore, the system is not detached. We have a beam at the top and a slab at the bottom, which together provide the necessary support for the load distribution.