To relieve that problem, on April 20, doctors cut out moon shapes under each eye and sewed in some thigh skin.
On Wednesday morning, when they removed the gauze that was sewed in with the stitches, the pain of it resulted in his popping an additional pain pill to get through.
He knows his tear ducts are working really well. " A few times tears have been running down from the pain," he said.
In a couple of spots on his hands, tendon is still exposed where the grafted skin isn't quite covering yet.
His fingers are fumblers right now. It's hard, for example, to open the small milk carton that comes with his meals, he said.
For four hours a day, he has finger-stretching therapy.
"It's crucial," said Lisa Rindal, 30, occupational therapist.
There also is mouth-stretching to be done several times a day.
"It's an ongoing battle," he said. An hour after doing mouth-stretching exercises, he can feel the corners tightening up again, he said. To help, a device is being made, a sort of skin-stretching retainer, that he'll wear whenever possible.
Even after Keller goes home, this stretching therapy won't end.
"This will go on for many, many months," Rindal said.
On Wednesday morning, Rindal, with gloves on, worked on his left hand while Michelle worked on his right. Rindal closed his left hand into a fist, so the new skin on the back of the fingers stretches.
Morning skin-stretching therapy goes on for two hours, albeit with breaks -- for the therapists. After 30 minutes, Rindal's and Michelle Keller's hands need a break.
He still needs help to take a shower. He tires easily. Stairs are hard. His appetite is pretty good, but he's lost 30 pounds. Doctors have explained that his body, in its intense efforts to heal, is using the same amount of energy daily that someone would use if they ran a marathon daily, Michelle Keller explained.
Rindal has been a therapist for five-plus years at the 20-bed burn center that gets patients mainly from out of state -- states such as North Dakota, Iowa and Wisconsin that don't have burn centers -- and from the Mayo Clinic.
She said she'll remember Keller.
Rindal said Keller has his down days, emotionally tough days, like all patients do. But she's accustomed to patients on those down days not showing up for therapy.
Keller never misses, she said. He's at therapy, regardless.
And he does more than that, even. In addition to therapy -- finger strengthening, as well as work on machines to improve his stamina and range of motion -- in the evenings, he takes hourlong inside walks with his wife.
Keller contends that Rindal remembers him because of the chocolate. He bribes her with chocolate to get those special T-shirts at the hospital that have the burn center's "Cool the burn" slogan on them, he said and laughed. He has a contest going with another patient to see who can get the most T-shirts out of her.
He has been outside, but has to avoid the sun. His grafted skin could easily be damaged and discolored from exposure.
Mohr said in about one year's time, Mark Keller will have recovered to about 100 percent of what he will be. Mohr said it's not impossible for Keller to become a deputy again. "It'll be a very uphill climb. But with Mark's motivation ... I'll be interested to see what happens," he said.
Mohr said there will be lifelong issues. The grafted skin is thinner, making it more temperature sensitive, pain sensitive, more prone to nicks and cuts. Mark Keller may someday have arthritis issues.
Keller said when his wife touches his arms, they're numb and yet the nerve endings go crazy, jangle, don't seem to understand how to interpret pressure on the new skin.
Michelle Keller is still able to be with her husband in part because her co-workers at Enable Inc. -- where she works with mentally challenged people --have donated vacation days.
And fund-raisers keep happening.
Keller is a volunteer firefighter whose paid profession is being a Burleigh County sheriff's deputy. His boss, Sheriff Steve Berg, recently was a barbecued-rib seller in front of Miracle Mart. Wilton also has had fund-raisers, and recently Keller's hometown of Center had an auction for Keller.