F-Secure, Windows Defender, Firewall(s) - yeesh!

I've a Dell Inspiron 1501 lap top that I've two days ago ordered enough RAM to max.  I use a high speed cable modem, connected to a Linksys, encrypted router.

My ISP, Charter Communications, provides subscribers with an F-Secure based program Charter calls "Charter High Speed Security Suite."  I've set it up so:

Virus and Spy Protection: HIGH

Internet Shield:  STRICT

Firewall is set to STRICT

Real time scanning:  all files

e-mail scanning:  Incoming and Outgoing

Automatic updates are enabled.

My ISP, Charter Communications, is non-responsive or auto-responds to subject advising me to perform tasks I've already specified I've done, and provided details of the results.  I have ZERO confidence in this company (they can't get the snow off my TV, either, but that's a whole 'nother forum!)

TODAY I finally set up the log.  I'd been copying and pasting scan reports.

I occasionally also use Windows Defender to scan my system.

MY CONCERN(S) AND QUESITONS:

1.  Every few days for the past week or two, I've been running a full system scan on my hard disk with the Charter software.  At times the scan report will ID virus/malware; other times the full scan detects nothing.  For example, three days ago, I ran a scan, and was clean.  Yesterday, I ran a scan, and the software reported "Malware found", identified three files infected with Trojan-Spy.HTML.Fraud.gen (virus), identified the files, yet took no action. 

Since I have the software set to monitor real time scanning for all files, how did that Trojan get in?

Why does the software not

2.  When I do a full system scan to include my hard drive and my external drive (which I use for storage, and to which I seldom connect),+system, +rootkits, the software consistantly finds either a virus or malware on my external drive.  For example, two scans ago it found malware on the external, I deleted those files, then defragged both the hard and external drives.  I used the external drive (without the laptop connected to the router).  Yesterday's scan found that same Trojan mentioned above.

Now did that get in there?!

3.  F-Secure's web site says I can't use Defender's firewall, so I'm using Charter's.  I instinctively feel Defender will do a better job for me, but may be influenced by my no-conficence with Charter.  IS WINDOWS DEFENDER ENOUGH PROTECTION TO USE AS STAND-ALONE PROTECTION?

4.  What do I need to do to get rid of the sneaky stuff, then set myself up so no MORE sneaky stuff sneaks in?

Bless the big fat heart of any of you who can help me!