Help tax

LG H1 01/05-09/05 work in Missouri, 09/05-12/05 work in Florida (He came to USA in 2001 with J1)

I am F1 work in Ohio whole 2005 (I came to USA 2001 with J2).

we report tax status: married joint or separate, which one is better ?
If separate, LG use 1040 form, can I use 1040 too since I pass the time test? If I must fill 1040NR form, can I get $5000 exempt, since I changed to F1 in USA? Thanks