1. Include, in the application, evidence to prove that the relationship is subsisting.
2. Based on information posted by other members, your wife will need to provide at least last 3 months' payslips and bank statements to support your EC application. But, that she is on probation shouldn't matter.
3. Your wife must provide evidence that she can maintain and accommodate you without recourse to public funds. Though declaring your savings may help, the decision to grant entry clearance will be based (amongst other factors) on your wife's ability to support you.
4. No.
After deducting housing costs such as rent/mortgage and Council Tax, your wife's net income must be at least £102.75 per week. See also
Maintenance and Accommodation
regards