^^^ His injuries were indeed minor, compared to what his family suffered. His most serious injury was a collapsed lung (which he inflicted on himself). He knew that it was survivable. His blood was also found on the kitchen floor by the cabinet under the sink where he knelt to get out the rubber gloves.
The DNA testing that was done in 2006 was more confirmation that he was indeed the killer. A bloody limb hair found in Colette's hand belonged to him. Also, both daughters were "tucked in" after death. That was sweet of those murderous hippies, wasn't it? (Sarcasm intended).
It was a rainy night, yet there were no footprints (save for the bloody one left by MacDonald), all the "weapons" came from inside the house. Supposedly, it was a home invasion, yet only the coffee table in the living room was disturbed (and experts have confirmed that it was top heavy, so had it actually been knocked over in a struggle it would not have fallen on its side as MacDonald had tipped it over). There was a magazine in the living room with an article about the Manson murders and a speck of blood was found on MacDonald's glasses, indicating that he had put them on after attacking his family to read about the other case.
There's lots more. The only "killer" was Jeffrey MacDonald. He's lucky he wasn't tried by the state; he could have received the death penalty.