I'm sorry, but I have to correct my own typing.

'Conventional' clothing means the type of clothing which is typical to an occupation or a sport. ('Conventional' could be used more broadly, but this would be a common use of the word.) As examples:

"When Michael works at the hospital, he wears conventional doctor scrubs."

"When Susan plays tennis, she wears a conventional white skirt and shirt."

Are these seven sentences correct and natural?

1. Music enhanced our enjoyment of the dinner.

Correct.

2. David was (chiefly / mostly ) interested in buying Persian rugs.

Both words are okay.  However, most native speakers would use either 'mainly' or 'primarily':

"David was mainly interested in buying Persian rugs."

"David was primarily interested in buying Persian rugs." (Less common, but more accurate.)

3. Sandpaper is an extremely coarse material.

Correct.

4. It was comparatively easy for him to learn baseball since he was already a cricket player.

Correct.

5. He is ( conventional / traditional ) in his clothing.

Both words are fine, but they have different meanings.

The following sentence may be closer to your intended meaning:

"He is conservative in his clothing."

6. In tropical zones it's exceedingly hot and humid.

Correct.

7. This room is used (exclusively / restrictively) by the faculty.

You could also say the following:

"This room is restricted to use by the faculty."

<em>Would you do me another favor and tell me the difference between conventional and traditional?</em>

'Traditional' clothing means the type of clothing which a race of people has worn for hundreds of years.  As examples:

"When Kiko attended her daughter's wedding, she wore a traditional Japanese kimono."

"When visiting other countries, many Arabic men are proud to wear traditional thawbs."

'Conventional' clothing means the type of clothing which typical to an occupation or a sport.  ('Conventional' could be used more broadly, but this would be a common use of the word.)  As examples:

"When Michael works at the hospital, he wears conventional doctor scrubs."

"When Susan plays tennis, she wears a conventional white shirt and shirt."

'Conservative' clothing means clothing which is not special, not too modern, and not too colorful.  As examples:

"When Tom had a job interview, he wore a conservative suit with a blue tie."

"At the company's celebration dinner, Mary wore a conservative black dress."