Hi there, welcome to the High Road
I have experienced both issues that you describe. The tearing of fletchings is easy to sort out. Quite a few possibilities:
1) The prod is not attached in a central position on the frame. Have a look at the front of the bow (obviously with it unloaded) and see if there is equal space at the prod aperture on either side. These prods can be mounted with some play in their position, so you need to get that central. You usually see a few millimetres of the frame on either side, that distance must be equal
2) The scope mount housing sits quite low on the frame and if you get regular crossbow arrows (factory fletching) then these have to be pressed down to fit under the scope mount housing. I found that this can lead to problems because if the fletchings are not exactly level on both sides, you can get wear on the fletchings from the lower lip of the scope mount housing. The solution is to have all your arrows refletched so that the fletchings sit a bit more forward. On mine they sit 45mm from the nock.
3) You need flat nocks, not moon nocks.
4) Loading technique. If you have short arms or are stronger in one arm than the other, you might be starting the loading procedure by grasping only one side of the string then pulling it up to meet the other hand. You can get off-centred loading like this (the centre of the string serving which should be in contact with the back of the arrow now makes contact with one of the bars of the string retaining mechanism instead). When you fire, the string realignes and you have some force imparted to the arrow which is not parallel to the frame. Correct loading technique is to use only three fingers of each hand, which must be placed on the string simultaneously, firmly against the frame and then the string must be drawn up evenly into the retaining mechanism. At all times your chest should be against the buttstock so that you use as much arm power as possible and you are aiming to use zero back muscle. When I load it, the only thing that moves is my arms. If you can't reach or you can't pull it like that then you need to see if a manual rope-cocking assist can help. Unfortunately there are no factory-made cranks or motors for the Crisbow crossbow to assist loading.
5) If your crossbow is compound then you might have a damaged cable-guide, or even a missing cable guide or one of the cables has come out of the cable guide and now you have stresses in the system which could mean the arrow is not acted on by a force parallel to the frame. You need to check that cable guide after each shot: a cable can jump out.
6) Worn centre serving. If the serving is worn (the white thicker string entwined around the middle of the bowstring) then you could have uneven materials acting on the back of the arrow or snagging under the scope mount housing. You need to redo the centre serving if that is the case, making sure it isn't too thick so that it has to be forced under the scope mount housing each time you load.
7) Make sure there are no rough nicks or dings on the crossbow track. Also check that no obstructions are present in the central track groove, because that will take out a fletching.
About the crossbow firing low:
1) These bows are very rough on scopes. You need to check that it can still be adjusted. I went through two factory scopes and one third party scope already on mine. If you can adjust the scope and can shoot lower than where you are hitting currently, then you might have a problem where the scope has been mounted in such a way that you can't get the track and the scope aligned. In your case the front of the scope will be too high in relation to the track. There are ways to sort this out, but I'm not the guy to advise on that procedure. Head over to the rifle forum and ask the dudes there how to do it.
2) If the scope is broken and you need to get a new one, you should make sure you get a genuine crossbow scope. The forces acting on a crossbow scope are more vibratory in nature than those on a rifle, so the internals need to be able to withstand that.
If you don't come right with that advice, then please post pictures of your crossbow, particularly the front prod aperture, the scope mount housing and an overview picture of your scope as mounted on the bow.
Good luck, good shooting, keep it safe and let us know how it goes.
when he sees this baby !! Cannot wait to bag a duiker the eco-friendly way ! 
