[Samba] Enabling LDAPS in Samba in a dual-DC setup

[Stephen]

Hi everyone, I have a basic SAMBA setup with a main AD DC ad1 and a 
backup AD DC ad2, running on Samba 4.5.16-Debian on Raspbian.

I would now like to enable LDAPS so my users can authenticate in other 
non Samba services using Active Directory. From reading the 
documentation here: 
https://wiki.samba.org/index.php/Configuring_LDAP_over_SSL_(LDAPS)_on_a_Samba_AD_DC
I understand that for the most basic LDAPS setup using the pre-existing 
self-signed certificate I need only add the following lines to my 
smb.conf to enable this:

tls enabled  = yes
tls keyfile  = tls/key.pem
tls certfile = tls/cert.pem
tls cafile   = tls/ca.pem

My questions related to this are:

1) Since I have a dual DC setup do I need to manually enable tls for 
LDAPS separately on the secondary DC, or will this be automatically 
detected from the primary and the settings copied over automatically?

2) How do I go about creating a dedicated user account that can be used 
with third-party services (in this case redmine) to access AD via LDAPS 
to retrieve user login credentials securely? For the avoidance of 
confusion here I understand the processes used to create a basic AD 
account. What I am specifically interested in is the particular 
combination of privileges or permissions i would need to set on a basic 
account to allow LDAPS access using this account. I believe I will need 
to create such an account to use with redmine since I have read that 
anonymous LDAPS access is not possible with AD.

3) What will happen in 700 days time when the self-certified certificate 
initially created by Samba on its first execution expires? Will 
everything just suddenly stop working suddenly and authentication in 
Redmine come grinding to a halt? How should I remedy this?

Thanks
Stephen Ellwood