The symbols are Rod Numerals ( https://en.wikipedia.org/wiki/Counting_rods#Rod_numerals ) turned sideways every other digit. When converted to letters reads:
defcon, 21, keyword, orrery
which leads to:
The symbols on the skull puzzle are actually from another “Chain of Death” cipher from The Shadow http://www.nku.edu/~christensen/section%205%20symbols.pdf You read it by following the chart and reading symbols in pairs starting with the secound symbol.
The message reads:
Which leads to:
That’s it for part 3. Part 4 has all the website clues.