hello

what are the best stations to use eve trader?

one would expect jita, but perhaps there are too many people there??

also, after scanning whole market, bot only has about 100+ profitable items to trade. is that normal??

in market analyzer, what is difference between total income/day and probably income/day

In my opinion Jita is the only station where you can trade (despite if you select low sec ships to trade).
Yes, about 100-200 items may be used to trade at a time, about 600 items show any income from time to time.

Total income per day is your income if you would buy then resell every item. Due to competitors, you will share thi income with others. Probable income is (X+1) part of total income where X is a number of competitors.

This is quite rough estimation. Profit as well as the number of competitors may change. One competitor may update orders twice more frequently then another. Item may be sold more frequently then bought and real buy-resell volume became lower then expected (e.g. implant sales. People sell implants to buy orders directly at the agent station. In Jita they dont sell implants to buy orders, but install sell orders. Regional volume is shown as high, but if you try to buy-resell implants, you will have problemss to buy implants and your income will be lower then expected).