How many paid submissions are possible to be made per month?

3.  How many submissions of this type are allowed per month for Free before I have to go on a paid plan?

You can have up to 10 paid submission per month on the free plan James.

When you get near the limit, you will be sent an email to alert you of this so that you can upgrade before the account gets disabled or you can decide to leave it as it is.

Once 1st of a new month is reached, all counters are reset to 0 so you can again capture 10 new paid submissions.