Nitecore makes good chargers, don't worry about burning your house down charging - I trust my Nitecore with batteries in it as much as I trust leaving my laptop plugged in. It's not good practice to leave batteries sitting on chargers, but I usually charge my batteries overnight. If I had a Trustfire charger or some no-name 2 dollar chinese wall charger I would stand guard with a fire extinguisher like I'm working at a supermax prison, but I have a Nitecore so I don't worry.
In terms of checking fakes with an ammeter, if you're buying from legit vendors you shouldn't worry (more than a few high-volume and really trustworthy vendors can be found here, I'm not a shill but I've never gotten a fake battery from Illumn or Wake and Vape). Don't buy from Amazon sellers or Ebay and you'll likely be fine.
The methods used to check amp draw on regulated mods is a little different than on single-battery unregulated mods - easy way to calculate amp draw in a regulated multiple-battery mod, check out this post by Mooch, the battery connoisseur, take the max wattage (or the max wattage you'll ever use in a build on your mod), divide that by the number of batteries in the mod, and use that wattage number and the mod's cutoff voltage number (usually 3.2-3 volts). Then take that wattage-per-battery and divide it by the battery cutoff voltage.
IE: Cuboid @ 200 watts. 2 battery mod, so 200/2 = 100w per battery. 3.2v cutoff voltage per battery. 100/3.1 = 32.26. 32.26 is max amp draw on each battery. Cuboid shuts itself off if the firing button is held for 10 seconds, so you'd pulse 32.26A max for 10 seconds max. Samsung 25R can handle that abuse all day long, easily. 30A pulses are usually what people use when they test and compare batteries, and 25Rs have been subjected to many of those 30A pulse discharge tests.
Cuboid @ 150 watts. 150/2 = 75w per battery. 3.1v cutoff. 75/3.1= 24.19A . Vaping at 150 watts in the Cuboid, if you could somehow fire the mod until the batteries die, you'd be fine. It's a hair below the max continuous amp rating of the 25R. If you could fire the device indefinitely, your chip in your Cuboid would fail before your batteries do. But you can't. Device will shut off at 10 seconds. You'd be more than find running at 150 watts.
Cuboid @ 70 watts. 70/2 = 35w per battery. 3.1v cutoff. 35/3.1 = 11.2A. Super duper safe, way under the continous amp limit of 25R. Not a ton of load. Super duper safe.
The biggest thing about battery safety is to get good batteries (which you did, 25R is a champ!), don't leave them sitting around all haphazardly (including unsecured in your pocket) so they don't have a chance to short against metal things, keep sets of batteries together ('marrying batteries', mark your batteries like 1A/2A and 1B/2B, so you always use A and B together, so their performance degrades evenly), don't use batteries with torn wraps (rewrapping is easy, and with color options, is an easy and fun way to identify married pairs of batteries), and work with safe amp loads (including checking for dead shorts - but since you are using a regulated mod, you don't need to worry about this, mod won't fire if it detects super low ohms, your mod will let you know if the ohms are too low and thus the amps are too high).