(how many explosive bullets a full hp rifle can shot before needing repairs)

It is considered a building block everything that can be built with a building plan and everything that can be put inside door frames, wall frames and window frames (not vending machines).

Handmade shells are always the cheapest raid method (sulfur wise) when a value is shown in the sheets.
When using handmade shells consider that Spas-12 deals less damage than other shotguns.

Splash damage is a kind of damage that is spread from explosives, these can have 2 types of splash damage:
the first type can deal damage to multiple building blocks and deployables at once (ex. rockets, explosive ammo);
the second type can deal "direct" damage to only one building block and "indirect" damage to surrounding deployables, but not to other building blocks (ex. c4, satchels).

When flame raiding it is necessary to use the fire balls created from the used tools as these provide extra damage, this said there are 2 types of fire balls:
the first type are produced by flamethrowers and incendiary rockets, they can deal damage to all flammable building blocks and deployables;
the second type are produced by incendiary arrows and incendiary bullets, they are smaller versions of the first type and are different in visual from each other, these can deal damage only to flammable deployables.

Most structures built with a building plan have a "soft side" that is less resistant to damage compared to their "hard side" (this comprehends mostly projectile damage and melee damage).

I test most of the stuff personally but many numbers are taken from Rust Labs [rustlabs.com] as it would take way too much time to get certain exact values.