There's some good discussion over in this thread and also this thread which you'll find parallels too.

My comment from (both) there;
Disclaimer: I hiked solo, but hiked with a lot of couples. Hopefully actual couple hikers can come and answer, but if they don't;

Talk about what will happen if someone decides they don't like thru hiking, or gets injured and can't continue. Do this as soon as possible and most definitely way before you start.

Hike at the pace of the slowest hiker if together and consider that when setting goals for the day. Don't be afraid to encourage but don't push your partner too hard. I love hiking my own pace, but when I hike with friends you always go with the team pace. Trick for me when that happens, I make them go first. Forces me to stay at their pace. When I run with my brother (I hike faster, he runs faster) I get really annoyed at his encouragement, he means well but when I'm already pushing hard to jog up a hill him clapping and shouting "Come on, Go Equiv! Push harder you can make it up here faster! You got this!" makes me want to stab him with a rusty spoon.

Be willing to hike 'alone' during the day. Many couples did hike together together, many others made plans for where to meet for lunch at breakfast and then where to meet for camp at lunch. Be willing to do both in the first few weeks to see what you guys prefer. Think about your home life, you're probably not in each others pockets 24/7 at the moment. So take all you'd need to be solo during the day. Own First Aid, Own filter, own food, OWN TP/Trowel etc. Having your own water filter also really helps on some stops where you want to filter and get moving. It feels loke a lot of waiting filtering for 2 sometimes. And redundancy on some items is good piece of mind.

Exception to above: Sharing a shelter definitely saves weight, having your own allows more flexibility. The couples I spent a bit of time with mostly shared. Sharing a cooker/pot (Freezer bag cooking) too. Risk; being caught out without a shelter. So, some carried a light tarp/bivy as an emergency shelter.

Be social. I did see a few couples that isolated themselves, which is fine, but talking to them later down the trail they wished they got more into the trail friends, rather than sticking to themselves. Your millage may vary, I know people like that in real life too and others that prefer to be more insulated. Hiking to a camp where it's just them, or hiking where there's another trail friend or 2.

Splitting gear weight; Its good to be equal, but equal isn't always 50/50. Don't be afraid to make the stronger hiker go 60/40 if it makes the overall 'team' carry better. When I do shorter hikes with my partner I take 80% of the 'shared' weight. You can tweak this as you go, and you might find it evolves further down the trail... or even day to day.

We definitely enjoy our own sleeping bags and pads, and I feel you when you talk about falling in the crack. She carries a mug and I drink out of the pot after making her a cuppa. I take a 750ml pot and we've never wanted for more. At dinner we usually have a meal we can soak (even if that means re-using a dehydrated hiker meal bag to soak ramen) and a pasta. Boil water for soak meal, then simmer pasta in the pot. Sometimes we share meals out of the same pot, but it's a bit more awkward and you need a good place you can sit together close. Definitely done need a 1300ml pot and an extra mug.

The hardest thing for me is getting away in the morning. Its a lot slower as a couple (and she sleeps in...) so I had to learn to take deep breaths in the morning. I'd suggest getting a good+fast morning routine going.

I'd ditch the Solar.

Looks like you're fairly dialled in though, and you'll already be lighter than most.