1) Base HP recovery is 0.5% of your MaxHP (including bonuses/penalties to such, and this is true for all of these) per 10 ticks. (An average character takes an action every 10 ticks.) If you are Infected, this becomes 0 instead.
2) Regeneration status gives you 3.3% of your MaxHP per 10 ticks. If you are Infected, this is reduced to 1.67% of your MaxHP per 10 ticks.
3) Ignite and levels of Poison cause 'degeneration'. Ignite, and each level of Poison, cause 4% of your MaxHP in damage per 10 ticks. This adds/subtracts with other factors. So a character with Poison 1 and Regen actually only loses a tiny bit per turn (+0.5 natural, +3.33 regen, -4 Poison = just under 0)
4) Warmth uses scary math and I don't wanna talk about it.
Suffice it to say more is better, but each "more" is slightly less "better" than the last.
The first target is +0.6% HP/10 ticks, and each additional Ignited target will be less helpful than that. (Remember too that Warmth also boosts SP regen, so this isn't all you get out of it anyway.)
5) Malleable will provide a 25% bonus to all positive modifiers to regeneration. So if you just have your natural 0.5%, it becomes 0.625%. If you have natural + Regen (normally 3.83%), that would become 4.78% Not much of a boost, but this isn't Malleable's main function anyway... although, notably...
6) The new Bright Blood passive triples your natural regeneration to 1.5% per 10 ticks, giving Malleable a bit more to work with. (This is in addition to Bright Blood's other effect of doubling MaxHP recovery from gaining XP.)