back-sweetening hard-rootbeer: keg bomb?

I am planning to make a hard root-beer for SWMBO. My original plan was to ferment sugar, honey, and light malt. Then back sweeten with splenda, add rootbeer flavor, and keg or prime and bottle.

A buddy of mine said "yuck- splenda!" and told me to back sweeten with sugar, and keg it. He told me as the pressure builds due to renewed fermentation, the yeast will stop consuming sugar, leaving me with keg-conditioned, sweet rootbeer. Will doing this over-carbonate my rootbeer, or worse yet, make a keg bomb (I suppose the pressure-relief valve would blow first)? or do the yeast generally quit before the pressure gets too out of hand?

Just use some crushed campden tablets at the end of fermentation and you can back-sweeten until your heart's content. You'll need to force carbonate, but if you're kegging, that's not an issue.

Or use Truvia or other Stevia product - better tasting than splenda.
If you use one of these, caution - stop sweetening before it's "sweet enough" - because in 3 weeks it will be sweeter. Don't know why it does that, but my personal experience back sweetening some Apfelwein 'just a touch' ended badly.

Hang Glider said:

Or use Truvia or other Stevia product - better tasting than splenda.
If you use one of these, caution - stop sweetening before it's "sweet enough" - because in 3 weeks it will be sweeter. Don't know why it does that, but my personal experience back sweetening some Apfelwein 'just a touch' ended badly.

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How much sweeter will it get, and how long does it take to reach this maximum sweetness?

OR

How sweetener much should one consider adding for 5 gal?