1) I could prove you that Hashirama has low chakra reserves as well, and he has Sage Mode.
2) Valid for "Toad" Sage Mode.
3) Tsunade had the Byakugou Seal - Strength of Thousands, but Tsunade is part Senju, so maybe this skill could be passed to Sakura as a legacy from the Slug Princess Sannin.
4) As I said again, Hashirama has low chakra reserves too.
5) She had three years to learn this.
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Proof of Uchiha/Senju clan members having low reserves of chakra:
You need Physical and Spiritual Energy in equal quantities to mold chakra
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The Sage created the Uchiha and Senju Ancestors. The panel that mention these clans clearly shows the technique "Creation of All things", since the Sage had the two Bloodlines, the Two Clans.
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This means that he had balanced Spiritual and Physical Energy when he was a single entity. When the ancestors were created, each one was disbalanced.
The Elder Son inherited way more Spiritual Energy, and way less Physical Energy. The Younger Son inherited way more Physical Energy, and way less Spiritual Energy.
This said, let's make some maths:
Chakra Unit = C
Spiritual Energy Unit = S
Phyisical Energy Unit = P
C = S + P
(These are the basis of my first link).
Now, the following link says the next:
Sage's Energy Distribution = S + S + S + S + P + P + P + P = C + C + C + C = Sage's Chakra Pool
Uchiha's Energy Distribution = S + S + S + S + S + S + S + P = C + S x 7 = Uchiha's Chakra Pool
Senju's Energy Distribution = S + P + P + P + P + P + P + P = C + P x 7 = Senju's Chakra Pool
Both Uchiha and Senju have very low chakra pool compared to the Sage, because their respective Phyisical and Spiritual Energy are unbalanced. The difference between them, is that the Senju have chakra with a lot of Physical Energy (that's the reason of why Hashirama has the power to give life with his Mokuton). In the other hand, the Uchiha have chakra with a lot of Spiritual Energy (Reason of why their Genjutsus and Ninjutsus are so strong, they have very low quantity of chakra, but this chakra have very high quality).
I hope now you understand why your statements are invalid.