Thanks for the tips, I'm further along now. I had seen the solar system puzzle, but didn't notice the dates on the bottom of the paintings. I main thing I missed was getting the letter of introduction. I did notice a strange 'glitch' or poor design.
Spoiler..
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I explored D'Allpins residence and found the correct example of his handwriting before I went to get the forged 'Letter of Introduction'. Then I went to the bistro and got the letter, but it didn't work, and I had to go back and get another one. This makes sense if you had the bad example of D'Allpins handwriting the 1st time, and the correct one the 2nd time, but since you can't indicate which sample to use for the forged letter, it assumes the bad one first! (even if you already have the good sample in your possesion) Now if you already know you have the correct one, why would you give Bebe the bad one the 1st time??