Clearing Out of Texas to Caribbean: Help Needed, Please

[SamVogel]

Apologies but not getting concise information from many resources tried... Q : What exactly is needed as far as clearance certificates/customs & immigration forms and health cert's in order to leave the USA (Kemah, Texas) in order to do a 6 mth cruise to Carib?
***from what I understand 1) TX State registration will suffice in most islands ( I cannot get USCG reg for boat as I am South African and boat was purchased in USA) 2)Obviously Passports, Crew Lists, extra photographs etc etc
*** Here it gets murky - a) Is a tax clearance cert needed? given my circumstance (S African, US boat) b) As my boat is still part financed the title sits with the bank... Do I need this document or is the deed of sale, bank documentation etc OK for most islands c) A friend insists that I need "Form 100" ... some sort of US Coast Guard "tracking tag" for bridges or entry points around the USA. Anyone know exactly what this is?
I am going to avoid Mexico due to the 2 day nightmares in order to check in and out , Zarpes etc ... will fly into Cancun again without yacht at later stage!
Lastly and slightly off topic... have quote from Lemma Insurance via Blue Water Ins... sounds too good to be true and they are a Russian company... any experience from forum on how well they pay out on claims? Thank you in advance for any assistance on a DEFINITIVE checklist of paperwork, documentation, certification for me to get out the USA, into most Carib islands and back into the USA again.