Did the merciful king go too far when he took his gift away from the debtor and put him in prison for not forgiving?Forgiveness of course; will God forgive all of our sins, yes he will, do we sometime stubbornly refuse to forgive people who have offended us yes of course, forgiveness takes time.
Will God take away our gift of salvation because of lack of forgiveness of course not, Jesus is teaching on the importance of forgiveness, not how to loose your salvation. There is only one unforgivable sin, and it is not un-forgiveness.
You have taken the application of this passage Matthew6:14,15, too far.
Did the Husbandman go to far to lop off branches that were in Jesus because they did not produce enough fruit?
Get used to it, if you are a disciple of Christ, you are going to be busy, because the HS wil be prompting you to know what good works Jesus prepared for you to do. So stay busy.