It looks like I am trying to fill up your dance card with so many responses to you.
I use GOOGLE as my search engine.
Under I found several significant sites covering this subject.
You will find a host of information there.
I am confident that you will be able to identify the downed airman you mention. As I recall, there were 62 or so men lost in combat from the black units, and I am sure that a roster identifying each will be available to you.
As for the question concerning the activities of colored troops in the Coastal Artillery, I checked:
WORLD WAR II ORDER OF BATTLE, Shelby L. Stanton, author, Galahad Books, NYNY, publisher
where I located any number of CA Regiments/Colored, which had been reassigned to Anti Aircraft Artillery duty.
Of these, only one had a record for serving in coastal defence, the 54th CA Regiment, (155 mm gun), (Mobile), (Colored).
The unit narrative indicates that the 54th was activated at Camp Wallace, TX, 10 Feb 41,and assigned to the First Army; relocated to Camp Davis, NC, 22 May 41; then to Fort Fisher, NC, 21 Oct 41; then returned to Cp. Davis 24 Nov 41; transferred to Fort Cronkite, CA, 28 Feb 42; then to Fort Ard, CA, 5 Apr 42; there assigned to the WESTERN DEFENCE COMMAND, 22 Apr 42; departed SF POE 6 Oct 42, to Pacific Theater of Operations. Returned to Fort Ard, CA, 30 Mar 44 for reassignments. The unit was never engaged in combat.
As for the black Dutch painter you mention, I have no idea.
Sorry, but that is all of the information I can muster for you.