Holy overkill. You can use things like 'lsof' or whatever to see what files a process has open.
But usually reading the manuals and sysadmin guides / tips for something is more effective than trying to reverse engineer / debug the program at a low level and hoping you'll figure it out.
SELINUX is one main area you must understand if you're having weird problems with things just not working with file sharing / networking. The firewall is another. You may just need to set up some correct SELINUX security contexts on your files so that SAMBA can access them. chcon, et. al.
iptables-save
also run the selinux troubleshooter utility and see if it is listing any AVC denials / SELINUX alerts, sealert, /var/log/messages, dmesg, et. al.
You could try turning off selinux to see if that helps the situation but usually the right answer is to employ it but learn to take advantage of its protective policies...unfortunately documentation on how / when to do that is a bit hard to come by still in many cases.