How To Limit User Quota Bandwidth to 10Gb/day

You might want to check the "delay_pool" directive listed in your example-- shouldn't it be "delay_pools" (with an 's')? I tested it locally (well, with Squid 2.7 not 3) and it caused all the delay_pools to fail.

Regarding question 1, the ACLs are OR'ed. Here's an example of how I use it to not use delay pools for access to internal resources through our proxy:

acl delay_pool_local_1 dst 192.168.0.0/24
acl delay_pool_local_2 dst 192.168.1.0/24
delay_access 1 allow delay_pool_local_1
delay_access 1 allow delay_pool_local_2
delay_access 1 deny all

Regarding question 2, you will want to put each acl directive on its own line.

For question 3, the simple answer is that based on your example, the "buckets" of bandwidth available to each client will always instantly refill. So they won't ever be empty.

The longer explanation is that the "buckets" will always refill at the rate you specify. A client will start out with delay_initial_bucket_level amount of bandwith. As the client downloads, data is removed from the bucket. So if you specify delay_initial_bucket_level 50, the buckets will start at 50% full. In your example above, the buckets always instantly refill (because they are specified as "100000/100000" for example) which means that the client is simply throttled to 100000. If you specified 5000/100000 then the buckets would "refill" at a rate of 5000. In that case, the bucket will refill at the normal rate even if the ACL isn't using it at the time.

NetLimiter can probably do the job.