Ok, so now we have a clear understanding of what the outout should look like. So you want values that have themselves as counter values to be 0 in the last column. I noticed in your output there was also a zero, presumably from an empty line. But I don not know why some parts start on a new line. To counteract the empty line and to cater for entries that might lack a reversed counterpart I used NF and reintroduced the +0 bit. I took RudiC's and Akshay's suggestions and made a couple of changes:

Code:

awk 'NR==FNR{T[$1,$2]=$3; next} NF{print $0, ($1 == $2) ? 0 : T[$2,$1]+0}'  file file