I have a nice but emotionally vulnerable client. I work towards developing his websites and his client's websites, and other kinds of project like graphic design, photo editing, etc.
When it comes to website development, I install the CMS and create a username and password for admin access, or back-end access. Then, the client requests the admin credentials, which I forward to him.
On several instances before, and now too, the client keeps changing his website back-end's password, denying me access to the back-end even before the project is completed and financially paid in full. This creates problem for me because I no longer have full admin access (for example, in WordPress CMS). Then what he does is, he takes over the whole CMS and sends me an invite to sign up for the website. This gets frustrating for me and creates more problem for me at work. I had told him before on several occasions that "please do not change password of back-end until the project is fully complete". But he tends to take everything personally and gets agitated when I tell him to do something he does not want to do. Over that, he takes over the whole back-end admin panel and starts playing with the website code and contents, sometimes complicating things further or messing up the website.
Now this is getting frustrating for me, and I am not so good at handling other people's emotional burden, especially my client (I don't think that is my job either - to deal with their emotions). I am also not getting paid for fixing problems that arise because he keeps playing with the code and contents of the website and messing them up. So, I just want to politely but firmly tell him not to change back-end user credentials and passwords until the project is fully completed and fully paid.
How do I deal with the client and tell him this? And how can I protect myself in the future if he damages the website before the project is complete (because he takes over the whole back-end admin panel and starts playing with the website code and contents)? That is also another concern that I have.
Please help.