SQL & PL/SQL :: Dynamically Filling Data In Table And Rebuilding Indexes Gathering Stats

I have created a table like below-

PROMPT CREATE TABLE tst_fetch_vendor_data
CREATE TABLE tst_fetch_vendor_data (
vendor_data_seq_no NUMBER NOT NULL,
study_seq_no NUMBER NOT NULL,
vendor_record_seq_no NUMBER NOT NULL,
control_column_seq_no NUMBER NOT NULL,
resolved_value VARCHAR2(4000) NULL,
original_value VARCHAR2(4000) NULL,
transaction_user VARCHAR2(30) NOT NULL,
[code]....

Its just a temporary table, in which data comes and goes. I am using this in middle of a process.I am using it in a process like below--

--EXECUTE IMMEDIATE 'TRUNCATE TABLE TST_FETCH_VENDOR_DATA DROP STORAGE';

insert /*+ append */ into tst_fetch_vendor_data
(select * from vendor_data vd
where vd.control_column_seq_no in
(select control_column_seq_no from temp_control_column));
dbms_stats.gather_table_stats('EPDSYSREP','TST_FETCH_VENDOR_DATA',ESTIMATE_PERCENT=>100,
METHOD_OPT=>'for all indexed columns size auto',CASCADE=>True);

code to use that table..This table can contain data from 0 to 108000000 records.Now my questions are-

1. How much should I select sampling size (currently its 100%)Can I use dbms_stats.auto_sample_size, what will be the effect?

2. dbms_stats is good approach or should I use dynamic sampling.

3. what about the approach using CTAS instead of inserting data through insert.

4. What about pl/sql table with index or with clause query.

5. Do I need to rebuild index after inserting data into table.