question about checking hydrometer reading in primary

my beer starting fermenting at about 20 hours. my airlock bubbled once a second for probably around two days straight. about 5-6 inches of foam rose on the top of the beer, and then on around the 3rd day it started slowing down. the foam started to receed, and the airlock bubbling slowed down. now it's bubbling about 2 times a minute, (this is the 5th day) and the foam has receeded considerbaly. but there is still an inch to two inches of foam substance on the top of the beer. will that foam eventually sink to the bottom? or can i go ahead and dunk my theif in there and take a hydrometer reading today, and then one in a couple more days to see if fermentation is complete?

the shorthand version here is,
1. will the foam on the top of the beer in my primary ALL sink to the bottom eventually, or do i just rack to secondary, and try to leave all the foam in the primary.

2. if i put my theif into my primary to take a sample for a hydrometer reading, and i get a lot of that foam into my theif, will that affect my hydrometer reading, or is this normal, and just what people do?

thanks.

The foam will drop after the majority of the ferementing has finished.
The foam will only effect the reading if it clings to the hydrometer and makes it more boyant. Just fill your trail jar to near the top and drop the hydrometer in. Spin it to release any clinging bubbles.

Don't forget to adjust for temperature if rewuired and don't put the sample back in. Us it for quality control purposes. Drink it!