Answer to Question 1
If the hematocrit of the pleural fluid is very similar to the hematocrit of the peripheral blood, then most likely the fluid is due to a bleed directly into the pleural space caused by trauma to the chest.
Answer to Question 2
Albumin is an important contributor to osmotic pressure. Decreased albumin allows fluid to seep into interstitial spaces. A transudate is caused by pressure pushing fluid through normal capillary walls (ie, not from capillary injury). Decreased albumin in the blood causes fluid to move from the capillaries into the pleural space, resulting in a transudative pleural effusion.