I am not with Laminar Research; just a flight simmer.
You haven't indicated if you are a Mac user or a windows based user and if you have a PC or a laptop.
The recommended location for the installation of X-Plane is the desktop. However, there are quite a number of flight simmers who have installed X-Plane on to a dedicated hard drive, preferably a SSD type. The size of the drive depends on your budget. X-Plane works quite well from this alternative location. Some also have additional drives and have installed multiple copies for various reasons.
For me, I run Windows on a purpose built PC with a dedicated operating system SSD drive with a dedicated SSD drive for XP10 , another SSD drive for XP11 and a 2 TB hard disc as my hangar drive as a backup for XP10 and XP11 together with any other software. At this stage there are no problems.
I am of the opinion I will and have sufficient disc capacity to meet my needs.
To solve your storage problem you may be able to consider the installation of an additional drive. If you do, I would suggest a SSD drive with a minimum 250Gb capacity
An alternative answer for storage capacity is to reinstall XP and only select what scenery you think you require at present. As part of the fresh installation only select the relevant tiles. You can always add additional scenery tiles in the future
In relation to the CH yoke problem there are others in this forum having trouble with this product. I am not able to provide a definitive answer to solve the problem In the meantime have a read of the answer provided by jroberts (Laminar Research) for a similar question at http://questions.x-plane.com/14395/yoke-does-work-the-ailerons-and-elevator-are-not-responding
Hope this all helps.