When to degas, add sulphite and Campden

I have 6 Gal of Apple Juice (store bought), EC1118, different types of sugar, primary for 10 days at 68 deg F, secondary 50 days at 68 deg F (doesnt taste very good - flat with aftertaste). Fermented good though - alcohol should be at 15%+ according to hydrometer. Still has some small bubbles but no burping in the air lock for over 30 days (SG 1). Next step - bulk age for a few months then bottle.
Question:
I will rack this weekend (read some stuff said to add some acid blend to help with flatness - so will add half suggested per directions on bottle at this time) and bulk age in another 6 gal glass carboy. So after I rack this weekend should I kill and sanitize (add the Campden and sorbate) and degas or wait until after the bulk age, then degas several times and add chemicals again later.
What process should I follow at this point.
Does this sound right: Rack, add acid blend, degas, airlock, wait a few hours, degas, add campden and sorbate, degass, airlock, 10 hours later - degass again, airlock - let bulk age for a month, rack, degas, airlock - let bulk age another month - bottle.
I have only made little one gallon stuff and drank to soon . Trying to make some decent wine this time.

I probably shouldn't even respond as I have only degassed once. I usually just bult age mine 10 plus months and the gas naturally come out.

I assume you are trying to "kill" the yeast or keep them from reproducing if you backsweeten. You say you want to add campden and sulphite in your post. I am assuming your meaning campden and sorbate if you want to neutralize the yeast. Campden is of course sulphite and you need to add sulphite and sorbate if your going to add sugar again at some point.

Yes I meant sorbate (changed it in the initial post). I most likely will not backsweeten, I thought campden and sorbate preserved as well as kill the possibility of re-fermentation. So the wine doesnt spoil.

My 2 cents: degassing isn't really necessary with apfelwein. If you prefer it degassed it's up to you though, personnally I like it carbed anyways.

I don't understand why your batch wouldn't taste good, both batches I made with EC-1118 turned out great. I'm thinking 15% ABV is a bit on the high side...

I did two stages of sugar to get the ABV higher. Brown sugar and granulated table sugar for the first 12% ABV with 1 pack EC1116 in primary then Racked after 10 days and used powdered brewers sugar and 1 pack of EC1118 for a month in the secondary, Racked and topped up the carboy (estimated at least 15% - probably 16% possibly 17%). I used water to top off this last time so I dont kick the fermentation back in with adding juice. After the next racking, before bulk aging, I may add some cheap Vodka (I use in my air locks) to top up to help stop spoilage and increase ABV.
So even if I dont degass it, when should I put in the items to stop spoilage and preserve (campden and sorbate) ? Right before I bottle or before I bulk age?
Yes I am making it strong for a reason. This summer I will freeze apple juice ice cubes and pour wine over them for a nice cool summer drink.
Ice cubes and apple juice ice cubes will water it down for me lol...
Thanks for your help.