Optimizing Large MySQL Table

I optimized a mysql table of 2 million records and about 500MB.. it took about 15 minutes.. However, on the same DB now i have another huge table of 88 million records, it size is 2.2 GB and it has about 30 MB to optimize... my questions..

1.- How can I speed up the optimization process so it can take the less possible time? any tweaks to my.cnf?

2.- Should I repair it using phpmyadmin or just from the shell?

3.- Should I stop http traffic during this optimization?

This is a dedicated db mysql server that handles a large VB forum with 5-8 users online average:

Code:
Intel Xeon 3.2 x4 procs, 32 bits, 4 GB ram
/etc/my.cnf

Code:
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
skip-locking
skip-innodb
skip-bdb
query_cache_limit=1M
query_cache_size=48M
query_cache_type=1
max_connections=1200
interactive_timeout=100
wait_timeout=300
connect_timeout=10
thread_cache_size=128
key_buffer=48M
join_buffer=8M
max_allowed_packet=16M
table_cache=2036
sort_buffer_size=1M
read_buffer_size=1M
read_rnd_buffer_size=2M
max_connect_errors=10
# Try number of CPU's*2 for thread_concurrency
thread_concurrency=4
myisam_sort_buffer_size=64M

# Add
max_heap_table_size = 48M
tmp_table_size = 48M
low_priority_updates=1
concurrent_insert=2

[mysqldump]
quick
max_allowed_packet=16M

[mysql.server]
user=mysql
#basedir=/var/lib

[mysqld_safe]
err-log=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
log-slow-queries=/var/log/slow-queries.log

On the other side, i have the same hardware for the webserver..