I will try to answer your questions here.
1.) For this we will need to check your admin panel. Please send us a temporary admin login.
2.) Open templates/your selected template/css/style. css then find below code
@import url(https://fonts.googleapis.com/css?family=Lato); @import url(https://fonts.googleapis.com/css?family=Open+Sans);
Change it to whatever the web fonts that you need.
Then change below lines to font family that you added. This code will be there in multiple lines and you will have to change all.
font-family: 'Lato', sans-serif;
font-family: 'Open Sans', sans-serif;
3.) Please check your PHP version it should be PHP 5.6 or higher. This is not requirement of our script but Facebook SDK need 5.6 or higher
If you want to remove Facebook login find and remove below code on footer.php
<a href="fbconfig.php" class="fb-login"><span class="fa fa-facebook"></span> Login with Facebook</a>
<a href="fbconfig.php" class="fb-login"><span class="fa fa-facebook"></span> Sign up using Facebook</a>