Can I change the value of those parameters (spoofprotect, syncookies, dynaddr_hack, notimestamps, nobroadcasticmpecho, ip_forward) from sysctl.conf file in systemd? 
Change network values from sysctl.conf
linux;networking;systemd;sysctl
From this link, I see that, these values can be edited.ip_forward=noipv6_forward=nospoofprotect=yessyncookies=noThe above variables can now be set in /etc/sysctl.conf which is acceseble via the System configuration menu, System variables. From this answer, I see changing net.ipv4.icmp_echo_ignore_broadcasts is not going to change anything. For timestamp, I believe you refer to the system variable net.ipv4.tcp_timestamps. As per this link, it is suggested to leave it turned on unless if you live on an extremely slow connection such as a 56 kbps modem connection to the internet.