In general, if it is important that workbooks are not changed unintentionally you should use the automation features built into Excel (
http://wiki.lazarus.freepascal.org/Office_Automation#Reading.2FWriting_an_Excel_file_using_OLE, or
http://wiki.lazarus.freepascal.org/ExcelAutomation/de), don't use fpspreadsheet in this case. Excel has so many features, and fpspreadsheet did never have the intention to support all of them. Therefore, it cannot be avoided that features are lost if an existing worksheet is loaded into fpspreadsheet, modified and re-saved.
1. This is not true. Maybe your spreadsheet is preformatted with wordwraps, and the columns are wide enough to not see them. Column widths in Excel and fpspreadsheet may differ because I don't know how Excel calculates column widths exactly. Please post a file which shows this phenomenon that wordwraps are added by fpspreadsheet (of course, post the file before it is processed by fpspreadsheet).
2. Hidden worksheets, like hidden columns/rows, protected worsheets/cells, encrypted workbooks etc. are features which are not supported, and I don't have plans to add them soon. But if you submit a patch I'd be happy to look at it.