Filter Multicast & Filter Internet NAT Redirection settings question

I am using an old wired Linksys BEFSR41 V3 Router to increase my security.
I looked up my cable modem and it is not a router nor does it contain a
firewall. I am using PC Tools Firewall Plus free firewall software on my
computer because it was rated in the top three. I was told that a router
increases my security because it has an "additional firewall".

Three Security questions in settings for this router:

1. Is it necessary to change the user name and password from default?

Settings under: Security > Filter > Default settings >
Filter Multicast: Disabled
Filter Internet NAT Redirection: Disabled
2. Would the security benefits of enabling these two settings sufficiently
outweigh the negative consequences (if any) that would result?

Settings under: Security > VPN Passthrough
Default settings IPSec Passthrough: Enabled --&-- PPTP Passthrough:
Enabled
PPPoE Passthrough: Disabled
3. Would the security benefits of disabling IPSec Passthrough & PPTP
Passthrough sufficiently outweigh the negative consequences (if any) that
would result?

I do not "Host" anything. I do not use a "VPN" that I know of. I just use
my computer to email and traveling the web and data stream for my investment
software. That is it, very basic internet usage.

Background info: Desktop AMD 4400+ 64X2 4GB memory 320GB HD Acer
(AM3100-U3201A) purchased new February 2008 -- 32-bit MS Vista Home Premium
SP2 -- MS auto updates on. Comcast ISP 12mbps service W\ Motorola SURFboard
SB5101 Cable Modem direct to computer.

Thanks for the help.

Bob