d is the 11th most frequent letter [1], so there are many other letters vying for the 8 main home row positions. However h is 9th, it's a good candidate for a better position, since it occurs in the two most frequent bigrams (th and he).
Since backspace is used far less than frequent letters by competent typists and enter is also relatively infrequent, it is probably best to put something like e on the thumb cluster, so that h can be on the home row.
It’s fine. I use mod DH, but it’s only a marginal improvement compared to getting an ergo keyboard (with thumb keys, key wells, split, columns stagger, etc.).
All the recent keyboard work I have done with the Pinecil and it's great. I use both a pointed tip and a chisel tip. The pointed tip is nice for most PCB work, the chisel for things like hand wiring.
The soldering work looks pretty rough (practice on a throwaway project first). Probably one of the TRRS or MCU pins is not well connected. Get out a multimeter and do a continuity check of all the connections. It could also be misconfiguration of QMK, but make sure the basics (hardware connections) are right first.
I found the position of the hand rests really weird from the pictures. But then I put my hands on a Model 100 that I have and they are in a similar position. Given that the layout and the keycap profile look the same as the Model 100, this pretty much looks like a plastic monoblock version of the Model 100.
That color though 😘, we should have more boldly-colored prebuilt keyboards than all the boring black/grey.
Someone listed one on an online marketplace (sorta like the Dutch craigslist) without a price. It had already been on offer for six days (probably not a lot of interest in ergo keyboards there), so I offered 150 Euro and he agreed.
Improved key wells, thumb clusters with more reachable keys, more compact and light (nicer for travel), switch choice, RGB backlight (handy for status report like battery life, active layer, Bluetooth profiles, etc.), function keys (which some people want), uniform key cap profile (can be rearranged when using eg. another layout).
I recently switched to primarily using a Glove80, but the Kinesis Advantage keyboards are great. There is a learning curve, but it is definitely worth it.
The Moonlander doesn't have a great thumb cluster anyway, so I wouldn't recommend it unless you have large hands. Prebuilts that you can get from Europe are (excluding keyboards without thumb keys like the Kinesis Freestyle Edge):
The Advantage360 does not really improve over the Advantage2, in some respects it's a step forward (variable split/tenting), in other respects it's a step back (tiring switches, Bluetooth connectivity issues), and in many respects it's stuck in a 30 year old design (same key wells, same thumb cluster where I can only reach 2 keys per thumb without weird stretches or moving my hand).
The Glove80 is really a step forward in many aspects
better key wells, better thumb cluster, better portability, etc. It's a contoured keyboard that takes all the lessons of the Kinesis Advantage and improves over it.
I'd recommend you to only practice a new layout on a column stagger keyboard if you have to use a row-stagger keyboard occasionally (type on someone else's computer, laptop, etc.). For me at least it was much easier to retain QWERTY muscle memory doing that, because they are completely separate for me now QWERTY-row stagger, Colemak-DH-column stagger.
(Though I am planning to move away from Colemak-DH, so my column stagger memory is going to be a bloody mess for a while.)