You do need to choose a password manager which will generate and store for you long passwords, like 20 characters.
I suggest you ditch Windows Defender, after researching your options. You can get excellent free protection with Qihoo 360 or Panda. Not up to their level but good are the three As: Avast, Avira, and AVG. If you want to get the best possible protection with a paid AV, note that they all allow a one-month free trial. You should never buy one before trialing it first. There are many giveaways of even the best paid AVs, sometimes for three months, sometimes for six months, and often for a full year, so you can be on the lookout. Another way you can gain acquaintance with the big boys in AV security is that most of them offer on their websites free on-demand scanners and removal tools that use the same signatures as their actual anti-viruses.