"(k) Question: "Happy is the one who guards justice and constantly does Tzedakah" - is it possible to constantly do Tzedakah?!
(l) Answer #1....
(m) Answer #2....
(n) (Rav Huna or Rav Chisda): "Wealth in his house; his Tzedakah stands forever" refers to one who learns and teaches Torah;
(o) (The other of Rav Huna and Rav Chisda): This refers to one who writes Sefarim (Tanach) and lends them to others."
WHY DOES THE ELUCIDATION OF THE FIRST VERSE BASE ITSELF ON A QUESTION - POINT OF ISSUE - IN THE VERSE, WHERAS THE ELUCIDATION OF THE SECOND VERSE DOES NOT?
How is the Talmud deriving from the verse, that it refers to one who writes sacred texts and lends them to others [or the other option]?
Your question is a very fine and perceptive one, pointing out the difference in the way the Gemara approaches these two verses.
(1) (a) It seems to me that the Gemara felt that the first verse simply does not make sense - how is it possible to do Tzedakah at all times?! One generally thinks of Tzedakah as meaning making a monetary contribution. Once the donor has given the money, his act is finished. Therefore the Gemara could not understand how it is possible to do Tzedakah 24 hours a day, seven days a week. The two answers to this question have the common factor that someone is supporting others 24/7 - either his own children or an orphan. These children are not only fed and watched over every day but also have a roof over their heads every night.
(b) In contrast, on the surface level there is nothing at all difficult to understand in the second verse. It teaches us that a person's capital and wealth can remain in his house, and simultaneously his charitable deeds will stand forever. This conforms perfectly with the Torah's outlook that one does not lose out by giving one's money to charity. In fact this was expressed by the daughter of Nakdimon ben Guryon (in the Gemara below, 66b) when she said that there used to be a proverb in Jerusalem that "Melach Mamon Chaser" - if one wants to "salt" one's wealth i.e. ensure that it remains intact, then the way to do this is continually to take something away from it to give to charity. Removing something from one's money to give to others is a guaranteed strategy for material success because as a reward for the Mitzvah of Tzedakah, Hash-m will give you prosperity in all your endeavors.
This idea was also elucidated by King Shlomo in Proverbs 11:24: "Some people scatter their money to Tzedakah and even more is added on." Therefore the Gemara did not have a question on the simple meaning of the second verse, because it fits in well with our belief that on the contrary, giving away one's money to Tzedakah is the best way of preserving one's financial assets.
(2) However, the above does not appear to be consistent with what Rashi DH Hon writes. He comments that one's capital remains in one's house but even so one's Tzedakah stands forever. Rashi seems to imply that there is some apparent contradiction between the fact that one gives to Tzedakah and the fact that one's wealth does not diminish.
The Iyun Yakov, printed in Ein Yakov, asks this question on Rashi. He answers on the basis of the Gemara in Sotah 21a which explains the difference between learning Torah and between all the other Mitzvos. If one does a transgression this may extinguish the merit one gained through one's Mitzvos. In contrast a transgression can never extinguish the merit of Torah study.
This then is the reason why it is not certain, even if one practiced Tzedakah, that one's prosperity will always remain because afterwards a person might commit a transgression which may remove the merit of the Tzedakah. Therefore we have to find ways of helping others with our Torah in order to ensure that the assets will always remain intact.
Now your second question can be answered. The Gemara knew that the verse "Capital and wealth in his house etc." must be referring to Torah aid because otherwise it would not be guaranteed that it might not erode one's wealth. The Gemara now finds two ways that one can help others in Torah and at the same time suffer no personal loss:
(a) If one learns Torah and then teaches it to others one might have thought at first sight that one is losing out because one worked so hard to understand the Torah and then gives over to others the hard-won results of one's labors on a plate. Our verse "And his Tzedakah remains forever" teaches that this way of thinking is a big mistake. The Maharsha explains this with the help of Gemara Ta'anis 7a which states "I learnt a lot from my teachers, and more from my colleagues, but from my students I learnt more than all of them." So someone who teaches Torah to others does not lose his Torah, but on the contrary he acquires more Torah through this, from the additional insights provided by his students.
(b) The other way of helping others with Torah and not losing anything oneself is to write Tanach Sefarim and lend them to others. The Maharsha points out that this interpretation fits in somewhat better with the simple meaning of the verse that one is giving out a material item - a book - to benefit others and this item remains forever but one still thereby acquires the Mitzvah of Tzedakah because one does not rent them out but rather lends them for free.
Thank you for your question which opened up new insights into this piece of Gemara.