In general, you don't need to repeat ている twice.
This looks perfect to me. You don't have to say 歪んでいて.
This sounds a bit weird. To me お腹が太る and お腹が大きくなる seem almost the same, so I don't get the point of saying both 太る and 大きくなる in this sentence.
And what is the intended meaning of this sentence? Someone's is getting fatter and fatter (progressive)? Or someone's abdomen has become large (present perfective)? If you mean the latter, this sentence would make sense. If you mean the former, note that 太っている almost never means "is getting fatter" (progressive). If you need to say "He is (currently) getting fatter and fatter" using 太る, you have to say 彼はどんどん太っていっている or 彼はどんどん太ってきている.