If you are increasing your dose step-wise and 130mgs didn't feel like enough then going up to 200mg isn't unreasonable, it isn't a huge dose - the reason we always suggest you go slowly is that people's response to opioids can vary hugely and you don't want to overdo it accidentally. nAON is correct though - you may be expecting too much from codeine. Some people get more from it that others - a decent dose still hits me hard despite having a fairly high tolerance, but even then I don't find it an especially noddy opioid.
DHC is very variable - some people get no recreational effects from it at all, others find it much more recreational than codeine. It lasts longer and is stronger mg for mg - charts (like the one I linked above) often say 2 x as strong but I don't find it to be quite that strong personally, more like 1.5 times. Work on the assumption that it is twice as strong, however, as you don't know how it will affect you and as I said it can vary hugely.
The CWE process for DHC is identical, yes. Often OTC DCH products (in the UK anyway) don't give you a clear filtrate due to the presence of titanium dioxide in the pills, so be prepared for a cloudy solution - just be careful you have filtered it properly.
Good luck! Be wary of stepping up higher than DHC, once you get a taste for stronger opioids the easiest one to acquire in the UK (usually) is heroin and it's a big jump from CWEing codeine or DHC to using that..