how to do change wit sed in bash script

Hi below is my bash script. which takes a source file and a token file, token file contains servicename:usage I have to find servicename in source file line by line if found then calculate memory usage then change -Xmxm with -Xmx\d{1,3}m. In below script bold line explain what to do much simple You can first under stand issue from below small part of script

  line="Superviser.childOpts:-Xmx128m" heapMB=750 line=($(echo $line|sed "s/${-Xmx\d{1,3}m}/$-Xmx{$heapMB}m/g"))  

So what is the wrong in above line

 #!/bin/bash
 sourceFile=$1
 tokenFile=$2
 if [ -z $sourceFile ]
 then
 echo "Please provide a valid source file"
 exit 0
 fi
 if [ -z $tokenFile ]
 then
 echo "Please provide a valid token file"
 exit 0
 fi
 #read token file and tokenize with : to get service name at 0 index and percentage usages at 1
 declare arr_token_name
 declare arr_token_usage
 count=0
 while read line
 do
 #here line contain :percentage usages
 OIFS="$IFS"
 IFS=$':'
 arr=($line)
 IFS="$OIFS"
 if [ ! -z $line ]
 then
 arr_token_name[$count]=${arr[0]}
 arr_token_usage[$count]=${arr[1]}
 count=`expr $count + 1`
 fi
 done # read source file line by line test with all the tokens 
 totalMemKB=$(awk '/MemTotal:/ { print $2 }' /proc/meminfo)
 echo "total mem = $totalMemKB"
 while read line
 do
 result_token_search=""
 #for j in "${arr_token_name[@]}"
 #do
 # echo "index=$j"
 #done
 count2=0
 for i in "${arr_token_name[@]}"
 do
 #here search token in line , if found 
 #calculate memory for this getting percent usage from arr_token_usage then use calculate frmula then device by 1024
 #then replace -Xmx\d{1,5}m with -Xmx
 echo "line1=$line"
 result_token_search=$(echo $line|grep -P "$i")
 if [ -n "$result_token_search" ]
 then
 percent_usage=${arr_token_usage[$count2]}
 let heapKB=$totalMemKB*$percent_usage/100
 let heapMB=$heapKB/1024
 echo "before sed=$line"
  line=($(echo $line|sed "s/${-Xmx\d{1,3}m}/$-Xmx{$heapMB}m/g"))
 echo "new line=$line"
 echo "token found in line $line , token = $i"
 fi
 result_token_search=""
 count2=`expr $count2+1`
 cat "$line" >> tmp.txt
 done
 done