Here are my findings with the newest build so far:
+ Volume is now changeable in calls; also with loudspeaker enabled.

+ Echo for 2nd person in calls seems to be gone, but need further verification.
+ No battery drain in standby and deep sleep/doze is working fine.
- CPU boosts up quite strong and mainly stays at high/highest frequency in the little cluster, when screen is on. It still seems to use all frequencies for very short times, though.
I think by now it is definitely stable enough to use as daily driver for me, as overall battery life seems to nearly match Nougat.
Thanks for the great work
@erfanoabdi
Btw:
LOSCoin warning still exists in latest build.
You can disable the warning of this bad joke via shell:
Code:
su
setprop persist.lineage.nofool true