Ha,Ha!!! Been married for almost 50 years, after we got married I bought her a 12 gauge and we duck hunted together for years. But I do remember she once said "Ill never be divorced, but I could be widow!" Words to live by!
You have a lot more options in veg than in flower. The Dr. Zymes will work, don't spray neem on plants in flower unless you like a nasty taste! If you find caterpillars, BT will work and not mess up the taste. I wouldn't worry too much about the occassional bite mark, hopefully they are...
2x4’s work great. Just put them in your catch pan to elevate above the runoff. If you leave them on the tent floor when you water to runoff it will be a mess and you’ll have wild rh swings.
A liter of water a day in a 6l pot is excessive. I’m sure you’ve washed out a lot of your nutrients unless you feed every day. Whatever the problem, it’s a non mobile nutrient, since it’s starting at the top. Most likely Ca, possibly S, or Fe too. Definitely could be ph related.
Not really, selective weed killers normally target either monocots (grasses) or dichots (most other plants), unfortunately both roses and blackberries are dichots. I would cut the rose bush off at the base, then when you prune back the blackberry in the fall/winter remove the rose.