In the fastest scoring of the match, Du Plessis and Temba Bavuma (64 not out) added 133 runs off 149 balls in an unbeaten fourth wicket partnership.
Dickwella made the most of his reprieve and went on to hit the day's sole six as he ended unbeaten on 42.
Herath took 5-93 but a brilliant 76-run knock by debutant Haris Sohail gave Pakistan a three-run lead over Sri Lanka's 419 at Sheikh Zayed Stadium.
Pakistan still trail the Sri Lankan first innings total of 419 by 153 runs with six wickets intact.
Spinner Rangana Herath finished with five wickets as Pakistan were bowled out for 422 at tea in their first innings on the fourth day in the first Test in Abu Dhabi on Sunday. The technology returned a verdict of "umpire's call", which no longer sees the unsuccessful team lose one of their two reviews per innings. The experienced campaigner got the danger man Azhar Ali out at the right time, as the top-order batsman was eying his hundred.
With Pakistan taking a very thin lead, a good performance from the bowlers was expected to push their case.
Sri Lanka opener Karunaratne had helped rescue his side from 61 for three before a mix-up with Dinesh Chandimal saw him sent him packing after a fourth-wicket stand of 100. "Actually I have played more games against Pakistan".
Four overs later, Lakmal got his second wicket as he trapped Mohammad Amir lbw for four runs.
In all Ali has so far hit three boundaries during his 297 minutes of batting. Apart from Herath's five-for, it was the duo of Pradeep and Lakmal who bailed out the Lankans from a possible setback after the hosts provided a solid start.
At present, Pakistan is trailing by 83 runs at a loss of seven wickets. But the middle order failed to fire and therefore the Sri Lankan bowlers made an inroad into the Pakistan line-up.