Fabrics: Rayon crepe was popular as was jersey knit. Think more like slinky knit rather then t-shirt. Velvet was also a huge thing, but it was thin and not all that thick like we have now.
Cotton voile was also popular, and with a slip could work well.
Colors were usually pretty much vibrant: navy, royal blue and red among others. White was an accent color for them usually. Also: green of any kind, beige, khaki, a dusty rose pink and mustard yellow.
Prints: florals are hard to reproduce with today's fabrics, especially on a short notice but you want smaller florals since the extra large one screams more of the 1950s. If you're wanting a print think polka dots, white on a color would be preferable (color on white is more of a casual summer look). While smaller dots were generally favored (not necessarily tiny pin dots, but small), large was also a popular choice that gained traction toward the mid-end of the 40s.
You can also go with plaid, the other staple of prints: gingham or border print (in another authentic fabric: broadcloth).
Solids were always popular. And you did not always have ensembles in the same color. Green/Red, Navy/Red, Khaki/Blue , Rose/Light blue etc. were very common and popular.
Trim is also a hallmark of 40s fashions. While things wore in the evening usually did not attach lace and rick rack, they used embroidery, soutache and pleating to achieve a more glamorous look.
On the fat and short thing: I'm built for 40s fashion and I'm fat. Biggest thing is the shoulders. If you aren't broad shouldered, pad them out.