Microsoft - Core Isolation - Memory Integrity

Hello,

I am a senior citizen (81 years old) who, for the most part, has NOT used the majority of the features on my HP laptop (such as Corona, Widgets, and 99% of the Apps). This has recently changed due to malware ending up on my laptop.

So, my question is...

In trying to beef up security on my HP laptop I came across Core Isolation & Memory Integrity. I Tried to turn on Memory Integrity, but each and every effort to do so failed (sadly)! ;o(

I bought my laptop from BestBuy, and while in store, asked GeekSquad to install Norton & MBAM Premium on my new HP laptop. My understanding is is that they had to disable Microsoft Windows Defender (Firewall & AV), hence could this account for the fact that I CANNOT turn on Memory Integrity? (as the security has been outsourced to Norton & MBAM)

I have had this laptop for 3 years and never used Core Isolation/Memory Integrity (because I was to naïve to even know that they existed), hence is Memory Integrity THAT important?

Question number two...

I have recently paid my ISP to swap out my Modem & Router for new firmware (replacement Modem & Router) plus new SSID and Wi-Fi password. I changed some of the passwords on my laptop on evening (late at night) and therefore had to restart my HP laptop...because it was late at night I forgot to reconnect to the Wi-Fi network when I shut down my laptop (I was very tired). The next morning I noticed that my laptop was NOT connected to the Wi-Fi network over night...does this make my laptop more vulnerable to attack? 

I thank you in advance for having taken the time to read my post, and of course, for responding. THANK YOU! ;o)