Another zone may be required
I believe you need another reverse DNS zone for the whole subnet, 1.168.192.in-addr.arpa.
In this zone, add NS records:
NS 1-30 ns1.yourserver.com.
NS 1-30 ns2.yourserver.com.
and a CNAM for each record you have control over, pointing to your 1-18.104.22.168 zone:
CNAME 1 1.1-30 (no trailingperiods, the full zone name is appended)
CNAME 2 2.1-30
CNAME 30 30.1-30
Therefore, given a lookup for 192.168.1.5, it will look for 22.214.171.124... which returns 5.1-30 (no period, so really equal to 5.1-126.96.36.199.in-addr.arpa) which will then look in your 1-188.8.131.52... zone and find the PTR record for 5.
Note the 1-30 zone prefix is arbitrary and can be anything really, but it helps with identication.