

Q1: What does "while you have 0 or less memory" in this card’s inherited effect mean, exactly?
This inherited effect's condition is fulfilled if the memory is at 0 through 10 on your opponent's side when a DP-based deletion effect activates on a Digimon with this card in its digivolution cards.
Q2: What does an "add X000 to the maximum your DP-based deletion effects can delete" effect do?
Such effects increase the maximum value shown for DP-based deletion effects. For example, while "Your Turn Add 1000 to the maximum your DP-based deletion effects can delete" is activated, "When Digivolving Delete 1 of your opponent's Digimon with 3000 DP or less" will allow you to delete an opponent's Digimon with 4000 DP or less.
Q3: If "add X000 to the maximum your DP-based deletion effects can delete" is activating, can the maximum be increased for an effect such as "delete 1 of your opponent's Digimon with DP less than or equal to this Digimon's DP" that references a Digimon's DP for deletion?
No, it can't be increased. You can't increase the maximum of a DP-based deletion effect that doesn't show a numerical value.
Lv.3 Guilmon BT19-007 U Rookie | Virus | Reptile [Start of Your Main Phase] If you have [Takato Matsuki] or [Calumon], gain 1 memory. --- [All Turns] While you have 0 or less memory, add 2000 to this Digimon's DP deletion effects' maximums.
Lv.3 Guilmon BT19-007 U Rookie | Virus | Reptile [Start of Your Main Phase] If you have [Takato Matsuki] or [Calumon], gain 1 memory. --- [All Turns] While you have 0 or less memory, add 2000 to this Digimon's DP deletion effects' maximums.
Lv.3 Guilmon BT19-007 U rookie | Virus | Reptile [Start of Your Main Phase] If you have [Takato Matsuki] or [Calumon], gain 1 memory. --- [All Turns] While you have 0 or less memory, add 2000 to this Digimon's DP deletion effects' maximums.
Lv.3 ギルモン BT19-007 U 成長期 | ウィルス種 | 爬虫類型 【自分のメインフェイズ開始時】自分の「松田啓人」/「クルモン」がいるなら、メモリー+1。 --- 【お互いのターン】メモリーが0以下の間、このデジモンのDP消滅効果の上限+2000。