I'm lazy so we'll use the Ascending Armour Class Rules which is the same as 5e. So with leather armour you'll have an AC of 12.

Your open stuck doors is 4 in 6 because you're strong :D
Hear Noise/Listen at Door 2 in 6
Find Secret Doors 1 in 6

As a thief your skills at level 1 are:
Backstab: Get ++4 damage to attacking an unaware opponent from behind

Climb Surfaces: 87%
Find and Remove Traps 10%
Hide in Shadows 10%
Move Silently 20%
Open Locks 15%
Pick Pockets 20%