You posted a firewall export with extensive uses of interface lists and address lists, but did not post those lists. We don't have crystal balls.
Anyway, if your firewalls rules have this effect:
Then yes, you won't be able to access the DSTNATed resource from 10.1.6.X. There is no "go outside and back inside your network". See this flow chart:
DSTNAT (#10) happens before the rules in the filter table chain forward (#14). Between those steps the packets don't leave the interfaces. At step #14, the destination address (dst-address) and destination interface (out-interface) have already been changed to 10.1.5.2 and (V35 LXC), and if your filter rules don't allow forwarding from the in-interface/src-address to that out-interface/dst-address, then the packets will not go through.
That's a reason why the standard defconf firewall, although it has a drop all from WAN rule, that rule has a special exception for connections that have been DSTNATed. This is the default defconf rule:
/ip firewall filter
add chain=forward action=drop connection-state=new connection-nat-state=!dstnat \
in-interface-list=WAN comment="defconf: drop all from WAN not DSTNATed"