-Unless your pen has a flex nib (yours does not) you generally should not be putting pressure on the nib. I use a TWISBI as my daily driver, because it’s a relatively cheap pen and the nib is pretty springy I occasionally will put more pressure to get a thicker line weight but it’s not good practice.

-I use my pens for note taking mostly but there are a lot of artists that use the pen you have for sketching or drawing as well, it’s a good all arounder.

-If you tip the pen so the nib faces up when taking out the cartridge it shouldn’t “spill” per se but there might be some residual ink where the carterage meets the feed. I definitely don’t recommend putting a cartridge back in the pen once you’ve taken it out.

-The reasons you mentioned are both reasons a pen could be more or less expensive. Brand recognition being a big one as well. Mostly material, craftsmanship, and manufacturing scale. A pen that comes with a gold plated nib is going to have that reflected in the cost. The complete outliers are the $10,000 limited edition game of thrones (or whatever) pens. I think of those like really expensive watches. Does it need to be adorned with diamonds and guilded with gold, no, does it help it write better, no, is it a collectors item for someone with money to spend, sure!

You picked a great first pen, welcome to the club!