Macbook Pro 2013 no longer boots
the only thing left no removed  - try removing RAM modules one at a time ( try each sodimm individually in either slot - do not forget to power unit off ( fans not spinning) as you meddle inside the unit ;) ... 
also - did you disconnect the dvd drive and did you inspect the logic board for possible water damage?

by the look - the unit does not pass POST  either due to dGPU or RAM/northbridge