Jack Edge

Hi all, I have been riding a Honda CBF125 M9 2009 for around 6 months now and the bike is overall in a superb condition with over 18k miles on it. It is important to note that the chassis of the bike is not straight from a prior crash + repair prior to my ownership of the bike. The trouble is recently I have started having problems with the wheel alignment and chain tension. One evening I had noticed that for no apparent reason the chain has come completely floppy and far looser than spec. I consequently undid the rear axle of the bike the next day and used the alignment guages along the side of the wheel correctly. After lining the guages up with a good chain tension, I noticed that, because my chassis was bent, the centre tread line of the wheel had no line up with the front wheel when both wheels were straight. As a result I now choose instead to look down the base of the wheels to align them rather than use the alignment guages at the side of the wheel, this seems to make more sense to me because the bent chassis would ruin the guages from accuracy anyway. After sorting out the problem using that method, my chain is now extremely clunky and feels tight (clearly sprockets are not in alignment). It then follows a few days / weeks later by becoming loose again. I fix it using the same method with the chain ending up in the same tightness (I am aware that this does wear the sprockets and chain links but feel that the alignment of the WHEELS is a more important thing to achieve). So in conclusion, if the WHEEL alignment is correct, the CHAIN (sprocket) alignment is incorrect. The same goes for vice versa. My question is this: 1) What has caused my chain to suddenly loosen like this after a while? 2) Is it more important to have the wheels aligned or the chain (sprockets) aligned? And, with a bent chassis, is it possible to get a combination of both? 3) (As a follow up to both) Whats the best way to fix a problem like this? All help is greatly appreciated!!!