I will give you such advice as my years have taught me, it's value to you may be nothing, or it may prove useful.
Your penis is not necessary to have sex. Your bride seems to love you, and there are many things you can do besides inserting your penis to grant her fulfillment.
There are also several things you can do to reduce the irritation of friction. I have, at times, actually had to bandage my penis, so I learned the hard way!
Pubic hair removal, both of you. It can be a significant irritant. Yours may not need to be shaved completely, merely short enough not to get 'into the action', but any close enough to the main event needs to be prevented from causing harm, and even stubble close to involved areas can be a problem.
For this reason I do not recommend shaving, but use of a depilatory (do spend the time to read the instructions. The Emergency Room, where chemical burns are treated, isn't always the best place to end an intimate encounter.), or (shudder!) waxing. Hell, some folks find the sharp, intense sensation of the wax being yanked quite titillating.
These grooming sessions can also become incredibly intimate, and personal, with each of you able to fine tune your partner to become even more attractive, according to your personal taste. So, don't hire it out, but each tend the garden of your earthly delights for yourselves.
You just might find the time spent more rewarding than coitus. Even that most forbidden of fruits, missionary position, with the lights off, solely for the purpose of procreation - and none of that kinky handholding! /sarcasm =p
Lubricant. This may, or may not, be of much help, depending on how you guys interact. I have found that after several hours, despite undiminished ardor, her natural lubricants can become in short supply, and friction increased. Also, some women just don't produce much lubricant naturally. Everyone is different, and it is fun to find where those differences can profitably lead.
Just applying lubricant can be an event in itself! Various textures, flavors (srsly), and even numbing agents, or 'heat' (again, I cannot caution you enough to be careful with either temperature, or spices, both of which can increase pleasure), can provide endless hours of satisfying exploration.
Tantra. Not every intimate moment needs to be culminated in a frenzy of aggressive pounding - although some may accept no substitute. There are various ways to 'play' that aren't intercourse, but can greatly enhance sexual enjoyment: blindfolds, light bondage, role playing, etc...
You have various appendages and mucous membranes, all of which some folks find sexy, or can at least be used to enhance sex from time to time, at least. Do what you must to reduce the damage to your penis, as needed.
Be forthright with her, and explain the actual issue that is causing you discomfort - and be honest, with both of you. Since you are already considering leaving the relationship because of this, there is no risk in laying your soul bare to her, even if a chafed penis isn't REALLY what is chapping your hide.
Not everyone has equal libido. My libido was never matched by anyone I ever met, and this has caused great suffering to me and those I have loved. I assure you that in hindsight I would have gladly reigned it in with far more vigor than I did, to spare them I loved the consequences that actualized.
She may also be willing to compromise. She might actually think this is simply what YOU want. She might prefer to play scrabble. You'll never know if you don't have an honest conversation, and give you both the benefit of a real chance to accommodate each the other out of loving desire to bless the one you love.
Ask her what her deepest, darkest fantasy is, and tell her you'll make it come true. Often, the most rewarding sex has little to do with, or less time on, your penis, granting you relief, while increasing both of your intimacy and pleasure.
Give it thought. If this is your sole complaint, I assure you, you have it easy, mostly because everything else is going so right, and this issue is relatively minor, and trivial to turn to your benefit, rather than allow to impede your happiness.
Not so many issues are.
If you have any specific questions, feel free to comment on a post, and request a more private means of conversation, if you would like.