McLeod was on target in the first-round clash along with Shaun Williams and 17-year-old substitute Brendan Galloway - for whom it was his first career goal - while Lee Gregory replied for the non-league Shaymen.
Waddock said: "It's a case of job done really, we're in the next round of the FA Cup so we're pleased with that.
"The first goal is always important and it was a fantastic goal from Izale as well, so we're pleased for him.
"This season in the main he's been on the sidelines but when he's come on he's done everything right in terms of his performances.
"He's worked hard on the training ground and he got his reward here - the first goal was an excellent strike and the second he's in the right place at the right time.
"To get the first goal settles everybody's nerves - they are always difficult ties.
"Everybody expects you to come out and be quite comfortable and win the game comfortably but that wasn't that case.
"You've got to give credit to Halifax for the way they went about their performance.
"Brendan (Galloway) has had a decent few months - he's gone away with England and done extremely well then he's come on here and scored."