#!/bin/bash

r=""
res=""
while read line; do
if [[ "$line" =~ ^(r[0-9]+f:[^ t]+)[[:space:]]+!+.+$ ]]; then
  r="${BASH_REMATCH[1]}"
fi
if [[ "$line" =~ ^(+[0-9]+..+[0-9])[[:space:]]+!+.+$ ]]; then
  res="${BASH_REMATCH[1]}"
fi
if [[ -n "$r" ]] && [[ -n "$res" ]]; then
  echo -e "$rtt$res"
  r=""
  res=""
fi
done < <(grep -E "^r[0-9]+f:|^+[0-9]+." /path/to/yourfile)

:/tmp$ bash script
r1f:O2+2PD=>2O-PD       +7.000000E-02  +0.000000E00  +0.000000E00
r2f:C3H6+2PD=>C3H6-PD       +9.800000E-01  +0.000000E00  +0.000000E00
r3f:C3H6+O-PD+PD=>C3H5-PD+OH-PD     +2.747319E-01  +0.000000E00  +0.000000E00
r4f:H2+2PD=>2H-PD       +4.600000E-02  +0.000000E00  +0.000000E00
r5f:H2O+PD=>H2O-PD      +2.492452E-01  +0.000000E00  +0.000000E00
r6f:CO2+PD=>CO2-PD      +5.000000E-03  +0.000000E00  +0.000000E00

#!/bin/bash

while read line; do
if [[ "$line" =~ ^(r[0-9]+f:[^ t]+)[[:space:]]+!+.+$ ]]; then
  r="${BASH_REMATCH[1]}"
fi
if [[ "$line" =~ ^(+[0-9.Ee-]+)[[:space:]]+(+[0-9.Ee-]+)[[:space:]]+(+[0-9.Ee-]+)[[:space:]]+!+.+$ ]]; then
  res1="${BASH_REMATCH[1]}"
  res2="${BASH_REMATCH[2]}"
  res3="${BASH_REMATCH[3]}"
  res1=$(echo $res1 | awk '{ printf "%.6E",$1*1.75 }')
  res3=$(echo $res3 | awk '{ printf "%.6E",$1*1.75 }')
fi
if [[ -n "$r" ]] && [[ -n "$res1" ]] && [[ -n "$res2" ]] && [[ -n "$res3" ]]; then
  echo -e "$rtt+$res1tt$res2tt+$res3"
  r=""
  res1=""
  res2=""
  res3=""
fi
done < <(grep -E "^r[0-9]+f:|^+[0-9]+." /path/to/yourfiles)

:/tmp$ bash script
r1f:O2+2PD=>2O-PD       +1.225000E-01       +0.000000E00        +0.000000E+00
r2f:C3H6+2PD=>C3H6-PD       +1.715000E+00       +0.000000E00        +0.000000E+00
r3f:C3H6+O-PD+PD=>C3H5-PD+OH-PD     +4.807808E-01       +0.000000E00        +0.000000E+00
r4f:H2+2PD=>2H-PD       +8.050000E-02       +0.000000E00        +0.000000E+00
r5f:H2O+PD=>H2O-PD      +4.361791E-01       +0.000000E00        +0.000000E+00
r6f:CO2+PD=>CO2-PD      +8.750000E-03       +0.000000E00        +0.000000E+00

#!/bin/bash
#takes $inputFile $pct
#note $pct is the multiplier expressed as a decimal

#global variables
#$w
#$newFile
inputFile=$1
#strip the suffix (.txt) from the inputFile name
outFile=${inputFile%.*}
pct=$2

function domath {
    # takes $value $multiplier
    local m=$(echo 1+$2 | bc -l)
    local theanswer=$(echo $1 $m | awk '{printf "%7.6En" , $1*$2}' | sed -E -e 's/[Ee]+*/E/g' -e 's/^([^-])/+1/g')
    echo $theanswer
}

function makechange {
    #takes $reaction $case
    #compose new file name
    newFile=${outFile}_$1_$(printf "%02g" $2).txt
    #make a copy
    cp $inputFile $newFile
    #change the appropriate line
    sed -i "${w[0]}s/$o/$n/" $newFile
}

#get all the reaction names
grep -Po "^r[0-9]+f(?=:)" Prob01.txt > stepA

#get all the figures and their line numbers in case duplicates occur
grep -Pon "^+[^!]*" Prob01.txt > stepB

for ((i=1; i<=$(cat stepA | wc -l); i++)); do
    reaction=$(sed "${i}q;d" stepA)
    figures=$(sed "${i}q;d" stepB | sed 's/:/ /g')
    w=($figures)
    #recompose the old string with double spaces as it was
    o=$(echo "${w[1]}  ${w[2]}  ${w[3]}")
    #compose the new string for each of the 4 cases
    for ((j=1; j<=4; j++)); do
        case $j in
            1)
                n=$(echo "$(domath ${w[1]} $pct)  ${w[2]}  ${w[3]}")
                ;;
            2)
                n=$(echo "$(domath ${w[1]} -$pct)  ${w[2]}  ${w[3]}")
                ;;
            3)
                n=$(echo "${w[1]} ${w[2]}  $(domath ${w[3]}  $pct)")
                ;;
            4)
                n=$(echo "${w[1]}  ${w[2]}  $(domath ${w[3]}  -$pct)")
                ;;
        esac
        #make the changes
        makechange $reaction $j
    done

done
#clean up
rm step{A..B}

thisScript Prob.txt 0.75