Hi Ahmed,
1. Typically a child with low weight for height AND oedema will be diagnosed as having "marasmic kwashiorkor" and under most (if not all) CMAM protocols this is an indication for inpatient treatment whether or not there are other complications or appetite for RUTF.
When fed with the correct diet 2+ oedema can be expected to resolve within 2-3 weeks. Generally oedema loss occurs more quickly with F100 / RUTF than with F75 so in the stabilisation centre progress may appear to be slower. As the 2+ oedema resolves you might expect a significant loss of weight (and weight for height). If the oedema is prolonged check that the therapeutic milk is being prescribed and prepared correctly or that the RUTF is being given as directed at home. Advise the carer not to use salt in any family foods that the child may be eating.
Since you used Weight for Height and oedema for diagnosis you should use those for discharge. The oedema should have been completely resolved AND the weight for height should be above -2 z-scores for 2 consecutive visits (assuming treatment is continued as an outpatient). If the patient is in hospital the oedema must have been completely resolved for a minimum of 10 days and the WFH be above discharge criteria for 3 consecutive days.
2. Firstly the child should be discharged according to the admission criterion. If the child was admitted on MUAC then discharge on MUAC, if admitted on WFH then discharge on WFH.
MUAC and weight respond in a similar way to treatment and can be expected to increase or decrease together in lock-step. There is no lag effect on the part of weight or MUAC. See this reference: http://www.ncbi.nlm.nih.gov/pubmed/26693279.
Typically only around 40% of cases of SAM that can be identified using WFH and MUAC will be classified as SAM by both criteria. If a child has a low weight for height (< -3 z-score) and a MUAC > 11.5cm at admission then you might expect the child to reach the "MUAC discharge criteria" of 12.5cm quite quickly, however since the child was admitted using weight for height you must wait until the child reaches > -2 z-score irrespective of what the MUAC measurement might be.
The length of time it takes for a child to be cured depends on how malnourished they were when they were admitted. A child with a MUAC of 10 cm on admission will typically take 10 weeks or more to reach > 12.5 cm for discharge. A child with a MUAC of 11.3 cm on admission will typically recover much more quickly. The same applies to children admitted with low weight for height. A child with a WFH < -3 z-score will recover more quickly than a child with WFH < -4 z-score.
In a study in Malawi all children admitted to OTP with a MUAC < 11.5 cm and discharged from OTP with a MUAC > 12.5cm also had a WFH > -2 z-score (many had WFH > -1 z-score).
I hope this helps