I read your second story (this) first and didn't see the 'challenge' in the comments until I got to the first one. Impressed you went for it!

Also had meant to say here that the flashbacks are nicely woven into the story and really add to it.

As for: "I feel that in switching between past and present tense, I'm kind of pushing the limits of my English skills."........such modesty :) - I think your use of tense works very nicely with the flashbacks. Pretty sophisticated IMHO!