I think this example would fall under the defence of property in proposed section 35 rather than self-defence in proposed section 34, but the issues are similar.
The trespasser comes on your property, and that's a wrongful act. Section 35, under the current law, gives the property owner some power to repel a trespasser in that circumstance. The question is whether it's necessary, whether it's proportionate.
Proposed section 35 refers to whether the act is reasonable in the circumstances. It does not provide the list of factors mentioned in proposed section 34 and does not refer specifically to the question of proportionality. My instinctive response to that example is that firing shots in those circumstances is a disproportionate reaction to the threat, unless the threat is greater than you have described it.
There's a well-known Ontario self-defence case from 1975, the Baxter case, where shots were fired in a situation like that and the court was concerned that this was an over-reaction to the threat posed by the trespasser. I think this provision would be easier to explain to juries and to apply if some of these elements were made more explicit.