Thoughts on need to backsweeten?

I've homebrewed beer before with some success, a number of years ago. I thought I would try a cider kit (which both myself and my wife can enjoy this time), but with no local sources of decent fresh cider, I'm trying a 24L cider kit made by Vinoka. Pretty straight forward, started it Jan 1st, looks like it's done fermenting (all bubbles have stopped, SG started at 1.038 and finished at 0.998, for a decent 5.1-5.2%). It's just starting to clear up and settle out from the top down, so my thoughts are turning to bottling in the next month. (It’s meant as a 4 week kit, not counting carbonation time.) Of course, being out of the game for a few years, I couldn't help but give it a quick taste while checking the SG. Lovely apple flavour and smell, but a little on the tart side.

Now, my concern is that, reading ahead in the instructions which came with the kit, it assumes I have the equipment to force cab, which I don't. I definitely do want to carbonate, so that leaves me with bottle conditioning. The kit comes with a small bottle of "flavour" which is meant to be added just before force carbonating, which adds a little kick of flavour and (more importantly) sugar to sweeten what was lost in primary. My problem is, by adding this small bottle of flavour before I bottle condition, that sugar will be converted to CO2 along with any priming sugar. I asked at the LHBS and they thought the sugar from the flavouring bottle plus and priming sugar wouldn't all ferment out as CO2, but I'm not sure that sounds right to me. So I'm looking for thoughts whether I should let that sugar from the bottle of flavouring do the job of priming sugar, and then add some non-fermentable sugar to back sweeten? Will the yeast turn all remaining fermentable sugar into CO2 in the bottle (if I added priming sugar too), or stop at some point and leave residual sweetness? Anyone ever tried a kit from Vinoka? Do kits ferment, age, condition much differently than fresh, no preservative added cider?

Could go with adding a nonfermentable sugar like lactose. Nots ure how the flavor profile would work with cider.

are you sure the flavoring contains sugar? most dont contain any fermentables.

Yeah, the bottle contains natural and artificial flavours, liquid invert sugar, etc. I think the reason most don't contain fermentables is because they don't expect me to bottle condition for CO2 after adding it. I'm not force carbonating like I'm supposed to with this kit, hence the problem. Dry we're ok with if the sugar all turns to CO2, but will the tartness soften over time? It's definitely going to be interesting whatever happens - add no sugar and I may get super dry, add non-fermentable sugar and I may get interesting flavours, add fermentable priming sugar and I may get bombs.