Omarsz

Yes, that should be fine. Their power consumption tends to lower slightly with time as the element heats up, as with most heating elements. There are heaters with negative temperature coefficients, but these don't tend to end up in kettles or washing machines, usually stand alone space heaters.

I will help you , will start with PM

Yes, that's it. Sadly, I don't have one of those in my collection. Weber and I are on record as stating that we'll attempt to patch at least the premature float bug on any firmware related to the PIP-4048 (excluding grid feed inverters and hybrids), but we need a manufacturer supplied firmware update file to work from. Your Axpert MKS II 5kVA qualifies, so keep an eye out for firmware with a version number of 71.XX.
[ Edit: linked to the "on record" post. ]

The MKS II 5k is a 450 V MPPT model, if I'm not mistaken. I'm not aware of any firmware update files for any of those models, so there is no patched firmware. If you can find a firmware update file for your model, then Weber and I can patch fixes for the charge bugs.
Edit: there is a small chance it uses the same firmware as other models, and those firmwares might be available for patching, or already be patched. What main firmware does it come with at present, or haven't you bought one as yet?

Just depends on loads. I have a 200Ah battery bank but the loads it needs to carry overnight are low. Nevertheless the small loads still results in a DOD of 30-40%. 
25 Ah is DOD of only 10%. One probably would want 10% to get reasonable life out of standby batteries. If one has proper deep cycle batteries a DOD 10% is perhaps not economically sound as one is not really using one's batteries.

My only problem with 58.4V is you are well above gassing voltage.

My AGMs absorb was at 56.4V and the Axpert's default for AGM gels is 56.4V so  56.6V  did not look out of place but really some basic guidelines would be nice.

That feels low to me. The documentation is sparse on this info, but looking at the one link, they provide this chart:

That seems to suggest an absorption voltage of around 14.6V is wanted per 12V increment, so 58.4V for absorption.
On the other hand this image seems to call for something lower... probably float voltage?

At 25°C. 2.23V times 24 is around 54V, so there I agree with you.

Morning @Omarsz
Attached is your batteries datasheet they are unusual in that they don't specify either a charging current nor an  absorb voltage.
 85.pdf
With that short coming in mind we will use standard values or existing values if they are not excessive.
Bulk charging voltage leave at 56.6V. 
Float charging 54.4 V
Battery Cut off voltage 47V
Back to grid voltage 48V
The charging regime is very high Gel and AGM batteries can accept higher charge but probably 60A is to high. Fortunately their rapid increase in internal resistance restrict current flow. I would try charging at 30A and if that is not problematic raise it to 40A and see.
Ac charging I would make also 30A.
Back to discharge voltage I would make 53 or 54V.. 
 
 

Hi Omarsz 
Welcome to the forum I have flu so it feels like my head is going to burst =-quickly
Max charging should be at 20A for now until I ahve looked at your batteries datasheet. 60 A seems too high.
roughly 48V is 50%. It would seem that there are several settings that are incorrect but I would have to confirm and I am just too ill to spend time looking at datasheets. Tomorrow maybe.