The looseness in alignment at the telescoping handlepost clamp is on all of them, you always need to align the top when closing the clamp. I recommend loosening the side clamp bolt at the handlepost base at the top of the head tube, and set that alignment such that, when you gently turn the handlebars to the right or left limit of the looseness up top (your choice), that it's then aligned correct, and you close the clamp; This will be easier than adjusting it for center each time.

Suntour?! Those folks still around? Some have fond memories of some of their lines, I think Suntour Superbe. But in terms of parts or features as advertised, Dahon seems to be worse than most, but this also may be because you looked online at a 2024 model and your 2021 is spec'ed per 2021, though it still might not be what was advertised.

There was a long thread, perhaps even a couple, about replacing the pin on Dahon hinges; One one, the pin would not extract and it was a blind hole up top, so they drilled a hole there to drift (punch) the pin out. I think that was also where they reamed it larger, and found a good subsitute pin from tool steel, a hardened steel gauge pin with precision ground finish. Ah, here's the thread:

Getting harder to fold into place. Danger or no?

Wheel true: Yeah, it should be right, especially with rim brakes. On my Dahons, it was not just out laterally (a quick fix), but also radially, which then affects all spokes. I removed the tire and tube, and having either the actual bike in a "workmate" (portable clamping work table) inverted and clamped to the seatpost, or the old frame or fork, I let the spoke tension completely down, evened up the nipples loosely by turns or view of the spoke threads, and set about retensioning the spokes, prioritizing radial runout, but still constantly checking lateral as well, little by little, half turn at a time (and holding the spoke with other hand to feel for spoke windup and not nipple turning), quarter turns, then really fine tuning it for radial, lateral, and tension. The rear wheel is dished so will not be same tension on drive side versus non-drive side, but tension on each side should be equal; Don't have a spoke tension meter? Neither do I, I just pluck the spokes to ring them, even tone is even tension, given the same length. My truing guides were just popsicle sticks clamped to the frame for both radial and lateral. Slowly brought all spokes up to tension. When finished, spun that wheel, didn't move a quarter of a millimeter. In the frame, this lets you get the rear wheel dish perfect without needed to measure, you just center the wheel in the chainstays. With the front wheel, periodically reverse the wheel, if that changes the centering of the rim in the fork blades, the fork is off in lateral blade alignment, or position of the axle dropouts. A good careful truing job, even and correct tension, and that wheel will stay in true a very, very long time, after many years, mine never gets out unless I break a spoke, happened twice in rear from not using a spoke protector disc and the chain chewing up a couple spokes (don't pull yours off, and if it didn't come with one, have Halfords put one on (tasteful clear plastic one), they are often required per safety regs).

I was never instructed on wheel truing, just learned by experience, taking it slow. I find it very satisfying, and owners will spend more time on it than the bike shop, and thus get a better result. However, check first that the rims do not appear to have any flat spots in the circle, and when truing, if suddenly the force to turn suddenly jumps up, stop; I didn't and permanently froze the nipple onto the spoke, had to cut it and replace.