If an answer is quite long how should we handle them to please the eye (improve readability)?
I think the format of your answer is fine. Making proper use of headers, font size, quote boxes, et cetera, are the kind of things you should do to make any answer readable, and you've done that.
I am not pleased with the length of it but I think it is quite complete (which is more important to me).
There's nothing wrong with a long answer. In fact long answers are often viewed as better than short answers because they (usually) provide a more in-depth solution to the problem than a shorter answer would. Making sure your answer is concise is important, but that's a problem that can be found with an answer no matter how long it is.
Should I split those solutions and make four answers instead of one or should this be the way it is?
If you have four separate and complete solutions to a problem than you're welcome to post them as separate answers. This actually has the added benefit of allowing users to vote on the individual solutions your propose, allowing users to see which solution is preferred. However don't post an answer into separate questions just because it's too long, and you want to improve readability. This would be the wrong way to go about making an answer more readability. Just make sure that every answer is a separate and complete solution to the problem if you plan to post multiple answers.