It has been a while since I completed Skyrim so I'll answer those TTBOMM.
1. Skill increases as you use them - simple. When each individual skill levels up, your overall level increases gradually. When you level up, you are rewarded a skill point which can be used to improve a specific skill from the galaxy tree. Only when some specific skills unlock in a tree, you may be able to use them. Classic case - forging the Daedric armor. You cannot forge this armor unless you have a 90 smithing skill. You can collect all the relevant ingredients for crafting the armor and yet not forge it until this smithing level is reached and the skill is unlocked in the tree.
2. You will find plenty of those in random ruins and barrows. Roam Skyrim as much as you can and explore!
3. Yes they do replenish the stocks once in a while. How often they do is something I am not sure of but all the mines replenish their ore veins after a certain period. Instead you can always trade ores from smiths. Ebony is one such ore which is available as ores very rarely but can easily be traded from vendors and smiths around the world of Skyrim.
4. Speech skill has nothing to do with getting married. You require the Amulet of Mara which can be purchased from a priest in the Temple of Mara at Riften. Wear this amulet and approach the priest and talk about getting married. He will give you a series of quests (three IIRC) relating to love and relationships (not romancing). Complete them. You should also find an NPC who is willing to marry you. There are plenty of them around and by default you cannot marry any NPC you may find in Skyrim (which btw can be modified using a console command).
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