Thought I would stop by and review your story. You were a lot of help to me in the past and I thought I would give my few thoughts.
This is a great story of redemption. The way you fed out the information, it caught me by surprise that Ron was actually donating a kidney to Sam. I had to go back and all the subtle hints fit. Well done. The theme of 'One Who Redeems Themselves' has been so overcooked it's hard to think of a plot that doesn't make me want to barf, but you handled this well by only revealing what Ron's true sacrifice was until towards the end.
Technically, I couldn't see any faults, although, as I'm sure you're well aware, I wouldn't be a grammar expert.
I do have a few suggestions. Please take these in the spirit they are intended, only to help improve your story. A lot of these are are tips that were passed on to me and I by no means implement them all the time.
Openning - The opening starts in Ron's POV. Throughout the first sequence your delivery of his POV is faultless with regard to only referring to matters Ron would know about and you never deviate into another POV. However, I still felt a detachment from the character. I'm not in Ron's head-space. This starts from the first clause of the first sentence. You start off telling how Ron feels instead of showing. Your next sentence attempts to draw the reader in through showing but that should be done in the first sentence. My suggestion would to reverse this. For example- first line "Ron's legs shook, entering..." or a brief inline thought conveying his feeling.
Showing and not telling - Much of the the story is told through dialogue and that's really good.This draws the reader in effectively and portrays the state of mind of the characters. When you transition to relaying information through narrative, at times you tell when you could show.
A couple of examples. When Ron initially sees Sam, you say he hasn't seen him in fifteen years, yet you relay Sam's condition matter-of-factly. Ron should be shocked at his jaundiced skin and gauntness.The shock should come through. Also, his reference to combat comes across as a little casual. I'm a veteran, but thank God I was non-combat and I have nothing but respect for those who endured firefights. I've talked to enough to hear the absolute fear they felt, the overwhelming noise and confusion. Death can come from anywhere, bullets, mortars, landmines artillery. I would try to weave those feelings in somehow.
Change of POV - You changed to Sam's POV towards the end of the story. Essential for the story. Couple of things to suggest. It's hard to know who's POV the story is being told from since it starts with dialog between him and his Mother. It's not until halfway through you realize it's being told from Sam's POV. The impact of the story can be improved by shifting the reader into Sam's head-space right from the start.
Another suggestion I might make is that Sam seems to forgive Ron awful fast. He might just be a better person that me, but if I had hated someone for nearly twenty years and been haunted by the things as done to him as you alluded to in the dialogue, I think I'd have a hard time coming to terms with Ron's sacrifice. I'm not suggesting you change it based on what I said, just think about it. I don't think it would affect the story line if Sam was left wrestling with his own thoughts of forgiveness. It may add to it.
Miscellaneous thoughts - Ron has become a Christian, entering into a relationship with God to the extent he wants to be led by him. Most Christians (in this sense,Trust me - I'm a Baptist Preacher's Son) would be creationists, so using the 5 million year old dating of the earth may be out of character for Ron even if he is referring to what Sam said. Ron would believe that information is a falsehood and wouldn't encourage it.
If you're wanting to gain a few words (words can be precious with these word counts) I noticed a couple of 'that's you could drop. Also in the sentance "...kind of woman with whom he wanted.." you could drop the 'with whom'. I noticed where you said "In truth, he did chat..." You could drop 'In truth' but I know how it is when you need certain phrases for your own style.
Anyways, that's all I could come up with. I hope some of this is helpful. Again, these are only suggestions. You are a very accomplished writer in your own right so you know best yourself. Let me know if you need any clarification on anything said.
Until Next Time,