Hello!
I can do the ffmpeg part.
I have a very good background on linux systems and I'm sure I can do the ffmpeg part. If you want, I can try installing squid (installing is ok, but I have to study it a little about the configuration).
I'm a computer engineer with more than 12 years of experience with PHP programming, having also worked as DBA for enterprise projects, mainly with PostgreSQL.
Please check my profile to see I've been doing many ffmpeg related projects recently. I can also help you with the correct ffmpeg command line to watermark your videos.
Keep in touch so we can discuss the details.
Best wishes!
Alex.