Hi,
Why do you want to get rid of nginx exactly? My suggestion is to move to nginx, and have a environment power by nginx, varnish and opcache.
I can also assist on debugging why apache is going down if that's your wish, but judging by your visits, I don't see why you don't use nginx.
Please lookup my profile and if you think I've got what it takes to get the job done, we'll talk more.
Thanks much,
Cosmin