So, I am doing some testing in live but only using microlots so just pennies.
Can the spread made your SL get triggered before it should or is there a slight difference between my broker and TradingView?
I am seeing some trades stopped out when according to TV they haven’t quite been hit.
What price is used for SL and TP, is it buy, sell or mid?
Yes, spread varies.
TradingView isn’t a broker. The feed will be stated on the chart. It’s best to only use your broker’s feed. Different brokers will quote different prices for the same pairs.
Mid is not used by brokers to trigger orders. The Bid & Ask will trigger SL or TP. Viewing the Bid or Ask depends on your settings.
Yes.
Usually, yes. And sometimes more than “slight”. (Why wouldn’t there be? Prices are not “objective,” they’re different products).
TradingView is a platform anyway, not a broker. The prices it displays as “TV prices” if you’re looking at it on TV’s own website, I think may come from Oanda, but don’t take my word for that, because it might be out of date.
Prices (as you’re asking about) in theory shouldn’t be “hugely” different, but they can easily be different enough to be relevant to whether your TP or SL are hit. And of course spreads can vary enormously.
Understand clearly that you’re not trading in a market. You’re betting against a counterparty on the price movements of the counterparty’s own products. I’m not saying that means you can’t do well! But be aware that that’s what you’re doing. 
The customer gets to choose that.
At least, you should get to choose. If you don’t, you may need a different broker and/or trading platform.
Just to be aware, the default setting for most charts is the bid price. Assuming that, if you are long the SL price will trigger at the same price which the chart shows. But if you are short, the SL will only trigger when the ask reaches that price: the ask is always higher than the bid. If you want the SL on a short position to trigger when the chart reaches e.g. 1.2233, and the spread is 1 pip, you would need to set your SL at 1.2233 + 0.0001 = 1.2234.
