I've created my module to fix these bugs. Here are some parts of the module. Thanks!

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# PROBLEM: there is an error when start and end periods are the same.
# SOLUTION: In build_ctx_periods, return the period_from_id with a list

# FILE: account.py
class account_period(osv.osv):
    _inherit = "account.period"

    # FIXED: There is an error if the start and end periods are the same.
    def build_ctx_periods(self, cr, uid, period_from_id, period_to_id):
        if period_from_id == period_to_id:
            return [period_from_id]
        return super(account_period, self).build_ctx_periods(cr, uid, period_from_id=period_from_id, period_to_id=period_to_id)
account_period()
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# PROBLEM: Target Moves filter functionality does not work in Financial Report, BS and P&L.
# SOLUTION: Include Target Moves in context.

# FILE: account_financial_report.py
class account_financial_report(osv.osv):
    _inherit = "account.financial.report"

    def _get_balance(self, cr, uid, ids, field_names, args, context=None):
        account_obj = self.pool.get('account.account')
        res = {}
        for report in self.browse(cr, uid, ids, context=context):
            if report.id in res:
                continue
            res[report.id] = dict((fn, 0.0) for fn in field_names)
            if report.type == 'accounts':
                # it's the sum of the linked accounts
                ### Use browse method to include context
                account_ids = []
                for a in report.account_ids:
                    account_ids.append(a.id)
                for b in account_obj.browse(cr, uid, account_ids, context=context):
                    for field in field_names:
                        res[report.id][field] += getattr(b, field)
                ###
            elif report.type == 'account_type':
                # it's the sum the leaf accounts with such an account type
                report_types = [x.id for x in report.account_type_ids]
                account_ids = account_obj.search(cr, uid, [('user_type','in', report_types), ('type','!=','view')], context=context)
                for a in account_obj.browse(cr, uid, account_ids, context=context):
                    for field in field_names:
                        res[report.id][field] += getattr(a, field)
            elif report.type == 'account_report' and report.account_report_id:
                # it's the amount of the linked report
                res2 = self._get_balance(cr, uid, [report.account_report_id.id], field_names, False, context=context)
                for key, value in res2.items():
                    for field in field_names:
                        res[report.id][field] += value[field]
            elif report.type == 'sum':
                # it's the sum of the children of this account.report
                res2 = self._get_balance(cr, uid, [rec.id for rec in report.children_ids], field_names, False, context=context)
                for key, value in res2.items():
                    for field in field_names:
                        res[report.id][field] += value[field]
        return res

    _columns = {
        'balance': fields.function(_get_balance, 'Balance', multi='balance'),
        'debit': fields.function(_get_balance, 'Debit', multi='balance'),
        'credit': fields.function(_get_balance, 'Credit', multi="balance"),
    }
account_financial_report()

# FILE: wizard/account_financial_report.py
class accounting_report(osv.osv_memory):
    _inherit = "accounting.report"

    def _build_contexts(self, cr, uid, ids, data, context=None):
        result = super(accounting_report, self)._build_contexts(cr, uid, ids, data, context=context)
        result['state'] = 'target_move' in data['form'] and data['form']['target_move'] or False
        return result

    def _build_comparison_context(self, cr, uid, ids, data, context=None):
        result = super(accounting_report, self)._build_comparison_context(cr, uid, ids, data, context=context)
        result['state'] = 'target_move' in data['form'] and data['form']['target_move'] or False
        return result
accounting_report()
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