Optimum Tyre Width 102kg Gravel Rider

I would say absolutely go wider but keep it a slick tread.

I'm currently 87kg and running Vittoria Terreno Dry 38mm (measure up 40mm) in the grey TNT carcass. They're slick enough that they roll along on road happily, but they are equally confident off road (yeah OK, on loose stuff you need to lean over to find the edge knobs more).

The carcass seems really robust also, I've learned to trust them more and more and there are some quite frightening noises coming from the wheels (and my downtube!) on some descents as I just sort of float and clatter over decent sized stones and rocks.

And, for what it's worth, Vittoria seem to be some of the better tyres in terms of going up tubeless, I can fit and remove them by hand although I still need to seat them first with a tube before popping one bead off, removing tube, installing valve and finishing off with a tubeless inflator. 

I would go wide. Even for a light rider, at 50/50 on/off road, I would focus on comfort and grip off-road over the slight speed difference on road. Add in your weight and I think you want as much volume as you can get.

A fat but slick(ish) tyre might be the best middle ground - I'm currently riding 47mm WTB Byways on my gravel bike and they're decent off road (provided nothing wet - they don't handle mud at all well) and roll pretty well on roads too. Not quite as fast as the 25mm tyres on my other bike, but really not far off.

You don't say if you're riding tubeless or not, but blowout implies your are tubed.  Go super fat if you are tubed and middle fat if not.  Rationale being you need a bigger chunk of volume to protect the tube from squishing too much under your weight, whereas a tubeless probably wouldn't have blown in similar circumstances. HTH.