If acyl chlorides are reacted with aqueous ammonia, will carboxylic acids also be formed?
Acyl halides react with water but usually not violently. The acyl halides are normally not soluble in water so the reaction is slow. Then, when the reaction proceeds, acid is formed and the pH decreases, reducing the reactivity of water.

Ammonia and amines are much more nucleophilic and react much faster with the acyl halide. This reaction is so much faster that it can be carried out in water. In this context it is called the Schotten–Baumann reaction, which normally proceeds with high yields. 

An excess of ammonia is required at least to absorb the HCl formed, but normally a huge excess is used. The acyl halide is more expensive than ammonia so we want to have it completely transformed to the amide. The excess of ammonia will also help to dissolve the acid, if it is formed in the reaction.  

The other points:


To separate acids and amides, extract with alkali. The acid will go to the aqueous phase and the amide to the organic phase.  Or, if they are small, recrystallize it. The amides are less soluble than acids. 
Huge excess of ammonia or simple amines is normally used. 
The reaction of water is negligible under these conditions.