score:7
If your train is canceled, you will be offered a means of substitution, generally the next train on that line that has enough room. Talk to the conductor if you need to meet a connection. There is generally no problem with boarding a later train if yours was canceled, except that if the next train is over capacity as a result, you may be asked to wait longer.
The same applies for major delays. Ask conductors if you need to make a connection. It's even possible to get reimbursed for a taxi if you miss your last bus home; nonrefundable plane tickets might be another matter.
There is a compensation program. You need to contact the appropriate service. There are several conditions to get a compensation.
Often, when SNCF assumes responsibility for the delay, there will be people handing out envelopes at the arrival station. If there aren't, ask at the station office. Fill in the form, put the ticket in the envelope (plus the note that says you were in a delayed train, which is mandatory if your ticket doesn't include a reservation) and send the envelope by mail. I don't know how that works if you don't have a bank account in France, there might not be a reasonable option to get the money.