So I'm in the middle of the pool build and we just poured the concrete decking. Before we poured the concrete I laid 2 in schedule 40 from the crawlspace stubbed up to schedule 80 for a future outdoor kitchen. In the middle of that conduit run there is a space I left to build a wood deck. Now I need to run power to the low voltage lights around the perimeter of the deck. I can't get under the concrete we poured to get back to the crawlspace so I'm thinking about digging down the 2 feet to the middle of that 2 inch conduit run and tapping into it in order to bring my low voltage wiring out from the crawlspace. Couple of questions.

1) Can I run low voltage ( 12V DC) and line voltage (120v A/C) in the same conduit? What if I use #10 THWN instead of the direct burial landscape cable while in the conduit? 600V insulation vs ?? with the landscape wire.

2) Assuming I CAN run both in the same conduit, what's the best way to junction into the existing conduit run below ground? I know the junction box would need to be accessible, I was also considering a t conduit body, which would also need to be accessible. Any other ideas?

Third semi- related question; I am planning on running the landscape lighting cables along the deck joists and stapling them with insulated staples. I will make the feeder connections with waterproof wirenuts but I was also planning on doing that inside a waterproof double gang pvc box. How should I enter the box that would be a weatherproof connection around the landscape cable? Any pics of what you suggest would be GREATLY appreciated.