I skipped the commands setting the mac address, I just set it via luci under network tab or uci.network.
Ive tried this before and it works for me, specially that my ISP is DHCP based (even though its static IP assignment), we all know that DHCP hates same MAC address when leasing a IP.
just use the "ip link add link " command
and then login to openwrt luci webpage and go to network
add a new interface, find the interface name you set earlier, then set it up as you like, and dont forget to set a dedicated MAC address for it since the default MAC is all just zeros. I use this to generate mac address for me http://www.miniwebtool.com/mac-address-generator/
once done it should be working as expected.
ps: since your macvlan interface is gone once restarted, just input those command on your startup (see in system >> startup) then all below on custom commands. just put your "ip link add link" command your entered before.
pss: if for some reason that your manual assigned mac address is not displayed on luci (still bunch zeros) restart openwrt will fix this, although this is just a cosmetic issue, since it my test the MAC address did recognized in my test DHCP server with the MAC address that I assigned.