Hi Fritz
Happy to help. Here are my responses.
My questions are,
1- Is it really worth LL+bowleg correction, or is only bowleg correction muuuuch easier?
To answer if LL+bowleg correction is worth it, you have to take multiple factors into account - like your initial height, extent of height neurosis, amount of time you have, affordability, type of social life you have. I was very short (at 160 cm) and I have height neurosis, had 1 year time for this procedure, and not so active social life apart from my family. So I see so much value in it.
I don't think bow leg is easier than LL. In either cases, your tibia is broken. You go through almost same level of trauma albeit for less duration in case of bowleg correction. Bow leg correction is usually on one leg at a time, and required 3 months per leg with 1 month gap (so total of 7 months). You can insist the doctor on doing both the legs at once, in which case it would be over in 3-4 months. Also, the external fixator that Parihar uses for bowleg is much smaller and very convenient as compared to standard Illizarov. So you can say bow leg correction is more convenient than LL. However, I only felt inconvenience only for 1st two months during LL. Then your body gets used to it and time runs faster. I can't believe that I'm already 6 months past my surgery. Time really flies 
Anyways, I'm giving you the facts and my experiences to help you make the right choice. So if you have time, then LL is not difficult as compared to bowleg correction, but inconvenient for sure.
Only last thing that to consider is full recovery. During LL, your legs are not as active as they normally are. So you don't perform all the leg movements that you used to perform when you're normal. Your muscles forget those movements when you don't perform them for long time (like 6-12 months). It takes effort, persistence and dedication to train them and get back to normal, but it's not very easy. So if you want full recovery, I suggest you do only bow leg correction because you'll be in that dormant state only for 3-4 months, so your chances of becoming normal again are higher and faster.
2- Which methods can be used for LL+bowleg correction at the same time? is the only method classic Illizarov for it? or with LON method is it possible to do LL and bowleg correction at the same time?
TSF, in my opinion, is the best for LL+Bowleg correction. It's full weight bearing, and very convenient with just 2 rings. Full weight bearing is very beneficial - it allows you to walk with full weight on your legs, even during lengthening phase. This is very helpful to fight ballerina and callus formation. TSF is a bit expensive, around 15k with Dr. Dhawan. So if money is a concern, you can go with standard Illizarov frames where bow leg correction is done post lengthening using Hexapod struts. Dhawan doesn't do Hexapod anymore (just FYI), he only prefers TSF and I totally see why he made that choice.
LON is not possible if you have bow leg, because it's not possible to put in a nail. To put it simply, you cannot put a "straight nail" in "bent legs". However, it also depends on the extent of bowlegs. If you have very mild bow leg, then I think LON is possible. If you're worried about wearing frames during consolidation, you can choose to get plating surgery post lengthening but most doctors are against it (even Dhawan) because it's not considered as stable and sturdy as nail fixation. I've recently been reading about stem cell therapy to speed up bone consolidation, but there is no concrete evidence so far. But if it works, then I would think that's a much better option to go as compared to Nailing or Plating.
3- I would like to gain 5-6 cm, and as i read your diary, it seems possible, but how long would it take to come back to normal life again. for example: walking without any support, riding a bicycle, swimming, dancing etc.
I cannot answer this question correctly because I'm not back to my normal life yet. But, I'm in touch with Phoenix and based on his recovery you can start walking without support with in 9 months. Note, he was able to walk with out support but he still had frames on. His frames got off after 1 year, and he was able to go back to his normal life. You'll be able to walk but you'd have very difficulty in jumping, running or dancing. You wont have your previous strength in your legs, it can take up to 1.5-2 years or even more to be honest, to run/jump/dance.
4- Would you get taller if you had just bowleg correction surgery? so as you wrote you gained 5 cm, but did you get it only from LL or did you gain any cm from bowleg correction as well?
I don't know. Please ask "varusilizarov" - he has done only bowleg correction. He might be able to provide accurate answer. But logically speaking, yeah I think you would gain some height with bow leg correction and the amount you gain would depend on the extent of bowleggedness (I just made up that word 
). The more bent they are, the more you'd gain.
I hope I answered your questions. Let me know if you need any more info.