Did you have a chance to review the LabKey install documentation I provided you earlier?
Your labkey.xml file is still suspect here. For example, you have the following listed as the first line:
<Context docBase="/scicomp/home/ytm4/LabKey15.2-39349.20-bin" debug="0" reloadable="true" crossContext="true">
This tells us that you are trying to use the unzipped directory that was created from the original zip file where the binaries were rather than setup a LabKey Server home directory as described here:
That docBase should be pointing to a /labkeywebapp subfolder from the LabKey Server home directory as described here under the appDocBase attribute:
It seems you have the required components (Tomcat, Java, Postgresql, the LabKey binaries), but you need to configure them properly now by moving the files/folders to the correct location and update the LabKey.XML file accordingly.
Can you review those two links I provided and go through them step-by-step. I know they're a little long, but if you follow along with both of them starting with the first link above, your install should work just fine.