I am new to OTRS and found it very impressive, though I have faced many issues while installing it

What I am trying to achieve:
In my already existing application, I want to give my customers the facility to create tickets from their control panel, so for this, I have created my own form to raise a ticket which is actually adding a ticket in OTRS using SOAP call. This is working fine!
Now, what I would like to do is to use my already existing DB of customers and support users (i.e. agents/users in OTRS) for Authentication instead of OTRS DB tables customer_user and users. Can I do it somehow? Can I use a different DB instead of otrs? As per few references on OTRS site ...
http://doc.otrs.org/2.1/en/html/x1553.html
I have done the suggested changes (changed the DNS, Table Name, Fields etc..), I was able to list my customers using my DB within the "Customers" section of the OTRS but I was not able to login using those details in "customer panel" and also I was not able to "Add/Edit" the customer data because it was adding/updating some extra fields like "create_time, create_by, change_time, change_by" which are not their in my table and are non-configurable and hard-coded in the DB.pm .
I think the reason why I was not able to login was the "encryption type" as I feel that OTRS is using MD5_CRYPT to validate passwords and I have stored my passwords in my customer table using MD5. Can this be the reason?
Also, Can I bypass the OTRS login somehow i.e. I want to give a "View Tickets" links in my "customer panel" along with "Add Ticket" and without doing any login to OTRS again I want to show them their tickets? Can this be done?
Can anyone suggest me on how I can make it workable?
Thanks