You can offset against other income in the same year, if you carry forward you can only offset against profits from same trade.
If you decide to offset against other income this year then you have to offset in full ie. use full amount of loss or until income is restricted to nil- you can restrict loss used so that you don't waste your personal allowance for example.
No. Trading losses brought forward can only be set off against the first available profits from the same trade.
You should see an accountant as it may be advantageous to use different accounting periods, although if your current profit is not much more than the threshold it is going to be difficult to reach an optimum solution.
Is it a trading loss or loss derived from sale of capital?
If trading loss, are you wanting to carry forward as profit is too low to offset losses? If so, the basic answer is yes - with the caveat - that there are different rules for different types of loss etc. You can offset sole trader losses aginst empolyment income too though, so an accountant would give you better, suitably tailored advice.