I have several repeaters, but the nodes also have (at least sometimes) connection to the gateway.
In the repeater log, I don't see the node connecting to that repeater. I guess that is shown in the log at some point, right?
Can you post logs where the node can see the gateway? What if it sees the gateway first, and then the gateway goes out of sight?
Did you try to set a static parent id?
The node is a very simple one. So I never considered boot loaders, as the node would not need changing sketches during it's lifetime. I have boot loading functionality on my other designs, this one is a minimal board. Any extra chip would beat the purpose of the word "minimal".
It's a dumb node for a reason
I liked domoticz (was very easy to set up and use). Together with dzVents scripting wasn't that difficult either. But I also had some problem with it lately, so I was actually thinking about switching to openhab (2).
I like those relays. Is that 3 different switched outputs? One thing I always liked about european wall switches is that they give you more room for components. I would like to use a similar type of relay for my in-wall switches, but with the way US single gang wall boxes are, there is a pretty narrow space constraint. I might be able to fit it if I did away with the thermal fuse, but I don't want to give up tat bit of added safety just for that.
The choice of MOSFET can be tricky. Seems that irlz44n was discontinued so you may need to find one adapted to the voltage and current you want to handle.
In all the cases you need to get a logic MOSFET too, meaning that they are fully open usually around 1 to 3V.
Also I'm sort of confused as it seems to me that L7812CV is a Voltage regulator, not a MOSFET. So if you are actually using that in the MOSFET spot it will definitively not work.
Especially if you are handling high current or voltage I would recommend using one from a reputable source for your MOSFET, I recently switched from mouser / digikey / aliexpress to mostly use http://www.arrow.com as you get free regular shipping, event if you order a couple of components (no affiliation to them whatsoever).