# I will most gladly spend and be spent

"I will gladly do any work and gladly allow God to permit people to kill me" 

# for your souls

"for you" or "so you will live well" 

# If I love you more, am I to be loved less?

"If I love you so much, you should not love me so little." or "If I love you so much, you should love me more than you do." 

# more

It is not clear what it is that Paul's love is "more" than. It is probably best to use "very much" or a "so much" that can be compared to "so little" later in the sentence.