I believe my music was copied in a popular hit song

Your personal attempt to contact the "infringer" is of no value. You must see Intellectual Property counsel re: the likelihood that Copyright...

The functional use of a pillow may preclude it from being a work of authorship and thereby a copyright interest. See Intellectual Property counsel.

Trademark filed and opposition

What are the grounds for their assertion that you will not use? You'll need to consult with Intellectual Property counsel. The filing date is...

Is it likely to get tracked for Credit card fraud in this case? PLEASE Help!

Use was theft. All use is likely photographed. See criminal attorney.

Is it legal to do a screenshot, screencap, or audio capture of copyrighted material for personal, non-comm., or internal purp.?

Use of a copyright property must be with permission. Contact to get a license. See Intellectual Property counsel.

I am wondering if having a 1 or 2 second long sound clip play during a video counts as fair use.

What is "Fair Use" - see 17 USC 107 - "comment, criticism, news-reporting, teaching, scholarship, research" - the use in a video might fall in one...

Do the rights to use stock photos and illustrations transfer from a design agency to a Client?

It depends on the contract between shop and company. See intellectual property counsel.

How can I file a DMCA take down report for infringements I cannot access?

The Asker might provide services as an Agent for the detection of infringement as does CEG TEK. See Intellectual Property counsel.

It is the Asker's IP address that the copyright agent has and it is the Asker who will receive the demand. The suggested defense of "it wasn't me...

The proposed use is Copyright Infringement. If every entity in the world just made 20-25 such shirts then there is a problem. If one is allowed...